[[quoteright:350:[[VideoGame/PrinceOfPersiaTheTwoThrones http://static.tvtropes.org/pmwiki/pub/images/Prince_and_Dark_Prince_79.jpg]]]]
[[caption-width-right:350:Left: Our hero. Right: Our [[EnemyWithout villain.]]]]

->''"But I'm not my "kind", not anymore -- your shadow leeches saw to that. I'm half Toa of Light, half Toa of Shadow. This was what you wanted, wasn't it? Toa consumed by darkness, Toa not hampered by things like mercy or morality. Well, now you can choke on it."''
-->-- '''Toa Takanuva''', ''Toys/{{BIONICLE}}''

The fight's not going so well for our hero. He's wounded and at the end of his strength, and his barely scratched opponent looks down at him and sneers. And then the hero somehow [[HeroicSecondWind suddenly taps into a massive hidden power source within him and unleashes a can of whoopass on his opponent]].

It's not exactly the hero any more, though. He's got [[GlowingEyesOfDoom glowing eyes]], some new FacialMarkings, [[CreepyMonotone a different way ]] [[PowerEchoes of talking,]] some [[EvilCostumeSwitch new threads]], and a lot less compunction about ripping someone in half. It's his Super-Powered Evil Side. Think of it as the EnemyWithin when it's not the enemy, or as [[JekyllAndHyde Jekyll and super-Hyde]].

Interestingly, notwithstanding the name, this character isn't necessarily evil -- he just seems like it because a superpowerful version of a normal person who has no compunctions about randomly destroying things registers objectively as "evil" on most people's scale. To be technically accurate, this is more of a Super-Powered Alter Id -- this personality is the [[PassionIsEvil physical manifestation of the character's basic drives]] without having to deal with the inconvenience of higher thought processes and morality -- but sometimes this character will have traits of actually being evil or even worse.

Keep in mind, of course, that once the Id is out of the subconscious it's not likely to want to go back in. Thus, the hero faces the very real [[SplitPersonalityTakeover threat]] of [[FreakOut not returning to normal]], each bout of AlternateIdentityAmnesia causing him to get [[AmnesiacDissonance more worried]] about the next. Generally speaking, though, he's usually safe unless he starts thinking EvilFeelsGood.

The narrative purpose of having a super-powered evil side is that it provides a way of saving a hero who is otherwise beaten but without making the hero look disproportionately powerful. It answers the question "why doesn't he just do that all the time?" with "because then the evil would take over." Additionally, if it leads to a FaceHeelTurn, it can serve the same purpose as GoodIsDumb in reverse -- it justifies taking one member of the FiveManBand or whatever and making him a match for his entire team while he has given in to evil.

This is the converse of WithGreatPowerComesGreatInsanity, seeing as in this case, [[PowerBornOfMadness with great insanity comes great power]].

One possible variation on this trope makes the Evil Side the ''original'' personality. This creates the odd situation of an "Evil" super-powerful monster whose "Good" not-as-powerful personality is dominant for whatever reason.

This is sometimes the reason to BewareTheNiceOnes. Compare with CrouchingMoronHiddenBadass, DemonicPossession, JekyllAndHyde and OneWingedAngel. Frequently overlaps with SealedEvilInACan and SealedBadassInACan. Contrast HeroicResolve, MyNameIsInigoMontoya, and HelplessGoodSide, although that last one sometimes goes hand in hand with this. May be caused by TheCorruption. One possible way of [[TookALevelInBadass Taking A Level In Badass]] and in many ways, this is what TheBerserker does.

SubTrope of EnemyWithin and SuperPoweredAlterEgo. If the Super-Powered Evil Side is triggered by the character's anger or rage, then it is a type of HulkingOut.



[[folder:Anime & Manga]]
* In ''Anime/MagicalProjectS'' Misao is normally a shy, physically weak and powerless girl, but when she transforms into her evil side, Pixy Misa, she becomes super confident and super competent. At full power she is able to easily defeat the heroine Sasami.
* Himura Kenshin from ''Manga/RurouniKenshin'' is a TechnicalPacifist in battle, fights with a reverse-blade sword and vowed years ago to never kill again. But if things seem to be getting out of hand even for him to handle (usually when his friends are in danger), his fighting style and mindset slowly begin changing into the highly pragmatic and ruthless Battousai, the assassin he was ten years ago. He switches the extremely humble ''sessha'' for the brash ''ore'', loses the ''de gozaru'' from his speech, his eyes turn gold and more slanted and he moves for the kill. In the anime, Battousai seems to be considered an actual personality Kenshin has learned to seal off by creating his rurouni persona - he has to punch himself in the face to push it back and revert back. In the manga, this gets lampshaded a bit when Kenshin remarks that his face muscles have cramped and he isn't able to end his permanent death glare.\\\
It's an unusual case, as in his current state Kenshin is actually much ''stronger'' than when he was the Battousai, having fully mastered Hiten Mitsurugi Ryu, including learning its ultimate technique, in the intervening years. But as the Battousai, he never held anything back, always going for the immediate kill. If he didn't stop himself every time the Battousai persona tried to emerge, though, he'd combine his increased strength with his former ruthlessness to become a near-unstoppable killing machine.
* Son Goku of ''Manga/DragonBall'' faced this early on with his Oozaru transformations. In this form he loses all sense of self while gaining immense strength and size; the best solutions found were to either cut off his tail or ''blow up the moon''. The transformation into the Oozaru, while generally a bad thing, did have two positive outcomes. One was the escape of Goku and friends from Emperor Pilaf; the second was Gohan defeating Vegeta... by landing on him.
** ''Anime/DragonBallGT'' takes Oozarus UpToEleven when Goku transforms into one as a Super Saiyan. Think a giant raging ape is bad? Try a giant raging Super Saiyan ape. Though Goku's able to come to his senses, which sparks his transformation into a Super Saiyan 4.
** The Super Saiyan state acts like this without proper training. The transformation occurs in a moment of pure rage, and the resulting personality shift leaves the Saiyan struggling with an overwhelming anger. In the Cell Saga, Goku and Gohan train in order to resolve this issue, making Super Saiyan as natural and comfortable as possible so they can maintain it without extra effort as well as retaining their own personalities.
** Frieza even comments on this when Goku beats him around as a Super Saiyan. He asks if Goku isn't being as cold blooded as he is, and concludes that Goku is still struggling to control the rage in him and that it's uncertain if he will win.
** Son Gohan's Super Saiyan 2 form is a truly chilling example. It is more than a little disquieting to watch the kindhearted and sensitive little boy we have come to care about over three sagas turn into a gleefully cold-blooded sadist when he achieves the Messianic power of Super Saiyan 2.
** In the Buu Saga, Vegeta falls under Babidi's mind control, becoming Majin Vegeta. However, it turns out that Vegeta is NotBrainwashed: he ''let'' Babidi put him under the wizard's "control" for the power boost that comes with it, and is perfectly capable of ignoring Babidi's commands (because they distract Vegeta from the reason he did it in the first place: fighting Goku).
** In ''Anime/DragonBallSuper'', we have Kale, a Saiyan from Universe 6. Her "Super Saiyan Beserk" form is just as violent as Broly's Legendary Super Saiyan form. Cabba could barely survive and Caulifla had to bail him out.
* ''Manga/{{Bleach}}'': Ichigo's inner Hollow is initially an extremely powerful, violent and monochromatic version of Ichigo. He ends up training Ichigo in how better to harness his Hollow and Shinigami power, but Ichigo has to beat him into submission to do it, or risk becoming a monstrous battle-frenzied BloodKnight as the price of power. Eventually, he learns how to harmonize with his inner power and can achieve his full potential without any loss of sanity and humanity.
** Which didn't help against Ulquiorra, which released the Evil Side after ''quite'' a massive [[TookALevelinBadass upgrade]], as he [[CurbStompBattle completely crushes]] Ulquiorra.
* ''Manga/InuYasha'':
** Inu-Yasha's demon side, although it could also be interpreted as WithGreatPowerComesGreatInsanity, as his bouts of insanity stem from having too much demonic power for his half-human body to handle. His EmpathicWeapon Tessaiga acts as a RestrainingBolt. Subverted in that eventually Tessaiga itself is so powerful that his demon side is actually [[PowerupLetdown weaker]] by comparison. (He was in fact given so powerful a weapon so he wouldn't need to rely on his own demon powers.)
** Suikotsu of the Band of Seven is a [[TheMedic doctor]] with SplitPersonality whose darker side is a sadistic, blood-thirsty murderer. It turns out that ''this'' is his true self, as well: he'd been good, gotten [[BloodKnight a taste for battle]] when defending his village, and became a mad killer of his own free will. The purifying effect of the mountain the story takes place on lets him revert to the decent man he'd once been.
* ''Manga/{{Naruto}}''
** Subverted where Jinchuriki can attain great powers due to being linked to their Tailed Beasts. However, only Naruto and Gaara are explicitly shown using this trope due to their DarkAndTroubledPast, all the other Jinchuriki can use their Beasts abilities easily, these two just ''lose it'', manifesting when either are emotionally distressed or when their lives are at stake. [[spoiler: Both manage to reject or tame these circumstances, the latter turns his into a SuperMode]].
** Sasuke and the curse mark. During the Chunin Exams arc, Orochimaru gave him a curse mark, which, once activated, turned the quiet, elite loner into a sadist who broke a guy's arms without a second thought. Creepy! "You seem quite attached to these ''arms'' of yours."
* In ''Manga/{{Hellsing}}'', Seras Victoria's berserker mode could be counted as her Super-Powered Evil Side.
* Lucy from ''Manga/ElfenLied'' is a variant of this trope - while she was originally the 'true' personality, she suffered a nasty head wound that caused SplitPersonality and left her [[HelplessGoodSide nonpowered good side]], CuteMute Nyuu, in control. The times when her 'true' self resurfaces fit this trope to a tee.
** In the manga, we learn that [[spoiler:Lucy - or rather, [[OnlyKnownByTheirNickname Kaede]] - is actually more of a superpowered ''neutral'' side, who's been listening to and partly controlled by a completely insane OmnicidalManiac ''third'' personality (created by either her Diclonius instincts or by [[BewareTheNiceOnes snapping]] as a result of [[KidsAreCruel the]] [[OrphanageOfFear torment]] [[BreakTheCutie inflicted]] [[AllOfTheOtherReindeer on]] [[MuggingTheMonster her]] when she was young, whichever theory you prefer) that wishes to annihilate the entire human species, if not all sentient life.]]
* Orson from ''Roleplay/RecordOfLodossWar'' is a Berserker Class and, when he gets angry, with the influence of the demon Hyuri he becomes an unstoppable killing machine that wields a massive claymore as if it were a toothpick.
* Sumire's Anti-Virus mode (called "Berserker") in ''Manga/VenusVersusVirus''. It's brought on by being shot by a special bullet. Berserker Sunire is supposed to only hurt Viruses however she is attracted to Lucia as well.
* Vash the Stampede's eponymous weapon in ''Manga/{{Trigun}}'' is triggered involuntarily by such events.
** There is less "evil" here than "EvilTwin pulled the trigger" or occasionally "moment of UnstoppableRage." Vash has never shown a Super-Powered Evil Side, although he does have the related tropes of CrouchingMoronHiddenBadass, an EvilTwin, and the occasional burst of aforesaid temper, after he witnesses a massacre or something else heinous.
** Livio from the manga plays it more straight, actually having a split personality.
* Yugi's powerful alter ego in ''Anime/YuGiOh'', Yami Yugi, is not actually evil, but he is a lot less concerned for the well-being of his enemies. Yami Bakura and Yami Marik, on the other hand, are both [[AxCrazy gleefully, psychotically evil]]. (Regular Marik isn't exactly a nice guy either.) In the manga, however, Yami is initially a GoodIsNotNice antihero who will dole brutal punishments out to the AssholeVictim of the week, the severity usually varying by threat but always a terrible MindRape at the very least. WordOfGod is that this due to millennia of imprisonment, but CharacterDevelopment and the influence of Yugi and co. put him in the GoodIsNotSoft category. This may have been the result of YuGiOh! being planned as a horror series and Yami Yugi being a straight split personality originally. This trope comes into play during the Doma filler arc of the anime, when Yami Yugi showcased his vengeful, darker side.
** Judai (Jaden), Fubuki (Atticus), and Kaiser (Zane) in ''Anime/YuGiOhGX''... except Kaiser doesn't gain an evil side as much a [[FreakOut new evil persona]].
*** Fubuki is possibly unique among this trope in that he has, twice, ''purposely'' assumed it, and had a rather good reason both times (well, good in his view, maybe). The first time he thought it might bring Kaiser back to his senses, seeing as he thought Kaiser might have been under a similar curse. (It didn't work, seeing as that was not the case.) The second time was due to his feeling that bringing Darkness (Nightshroud) back was the only way to answer [[UnfinishedBusiness the questions]] tormenting him.
** Displayed in ''Anime/YuGiOh5Ds'' with the Dark Signers. Most of them became evil due to BlatantLies told to them by the Earthbound Gods, and most [[RedemptionEqualsDeath came to their senses before it was too late]]. Aki (Akiza) is another example, although a HeelFaceTurn in her case didn't cause her to lose her powers. (In fact, it actually made them more benign, eventually.)
** And Yu's (Yuya and his counterparts) of ''Anime/YuGiOhArcV'' have what is colloquially known as Berserk Mode, in which their eyes glow and they become enraged and battle-thirsty in order to win a duel. Yuya develops one after absorbing his alternate dimension self, Yuto. It comes with glowing red eyes, a CreepyMonotone voice, and MajorInjuryUnderreaction to being repeatedly hit with a monster's flamethrower. The persona has given Yuya some powerful cards (notably Odd-Eyes Rebellion Dragon). But the more powerful it gets, the more violent and malicious it becomes.
*** Yuya actually has two established evil sides; Yuto, who while otherwise benevolent, will act on his ([[ThePurge completely]] [[WarIsHell justified]]) hatred of Fusion and Academia. The other is an unknown darkness that's [[SplitPersonalityTakeover trying to take over both Yuto and Yuya.]]
*** That unknown darkness living that's trying to take control of both Yuya and his counterparts? [[spoiler: That's the demon, Zarc, whom Yuya, Yuto, Yugo and Yuri all used to be part of, until Ray split him, the universe and herself into four pieces each. Zarc eventually gains full control over Yuya and his counterparts and it's not pretty!]]
* The eponymous warriors of ''Manga/{{Claymore}}'' constantly run the risk of becoming "Awakened Ones" when using their powers. In that state, they become their Super-Powered Evil Sides without any chance of turning back to their original forms.
** The twist is [[spoiler:HeroicWillpower lets the sufficiently motivated come back from the brink and retain some control after completely transforming]].
* Played with in ''Chobits''. Robot Persocom Chi has a personality living inside her called Freya. Freya always wears darker clothes, sports far less innocent expressions than Chi and is the one to take action to defend Chi when others threaten her. She's not evil, just less innocent than Chi and the holder of the answers to many mysteries of the series.
* Quiet and retiring Haru's alter ego, "Black Haru," from ''Manga/FruitsBasket'' is a humorous take on the trope. In the anime (or early in the manga), at least. It's played for some serious drama later in the manga.
** Along the same vein, that goes for the brief 'cameo' of [[spoiler:"Black Yuki"]] in the later chapters as well.
* When Yuuri from ''LightNovel/KyoKaraMaoh'' reaches an appropriate level of moral outrage, he involuntarily transforms into a larger version of himself with cooler hair, amazing magical powers and a thirst for justice.
** ...who almost always ''says'' he's going to kill people, even though he 'dislikes bloodshed', but has no confirmed kills, and is usually confirmed as not having hurt anyone. Once he sentenced an UnluckyChildhoodFriend and her quarry to go on a date. Another time he mistook an assassination attempt for an earthquake and saved everybody, even the enemy soldiers who'd been trying to kill him. Also, he has been known to say nonsensical things about fire brigades etc., just like Yuuri always does, just in a serious, booming way.
** In the manga he gets a lot closer to the 'evil' line, but is a lot less divorced, in terms of identity, from normal Yuuri, whose lifelong tendency to a really violent temper is underlined. But the manga is darker than the anime. And Yuuri accidentally stabbed Wolfram half to death a while back in the novels. Genre Woobiefication?
* When Kazuma of ''LightNovel/KazeNoStigma'' taps into his evil side (really a reversion to his old behavior in his backstory), he will do whatever it takes to accomplish his goals, no matter who he has to hurt (or mind crush!). [[spoiler:Kazuma may actually be a subversion if Ayano is correct in her analysis when she faces him to try and stop him from going on his rampage. She states quite clearly that he used to be so overwhelming that it seemed to be stupid to be afraid of him. Because she was afraid, it was proof that he was weaker than before. In any case, he's still very kick ass.]]
** [[spoiler: She's right. When he's in this state he's basically letting his anger and pride control him (something he had often warned others against), lacking the ability and focus that he'd shown in the rest of the series. This fight is also the first time that she gets the best of him, first [[WhatTheHellHero calling him out for his behavior]], then landing a solid hit that knocks him off his feet.]]
* In ''Manga/JoJosBizarreAdventure part 5'', the protagonist Giorno Giovanna develops a new stand "Golden Experience Requiem" which is intelligent and can act on its own, and completely destroys his enemy Diavolo, causing him to experience death over and over again for all eternity.
** Diavolo himself inverts this with [[spoiler:Doppio, effectively a Powerless Good Side]].
** In part 6, Weather Report gains one when he recovers his memories in the form of Heavy Weather, [[spoiler:which makes people believe they are turning into snails using [[ClapYourHandsIfYouBelieve subliminal messaging]], which leads to them actually turning into snails [[YourMindMakesItReal in a serious case of mind over matter.]] ]]
* Ginji's Raitei persona in ''Manga/GetBackers''. [[spoiler:Kazuki]] also has one, when [[spoiler:he releases the seal on his Stigma eye.]] The same way Ginji is the "Thunder Emperor," he's "the Prince of Terror."
* In ''Manga/DaaDaaDaa'', you can see a crystal-clear example in Christine, the older Hanakomachi... when a girl (human, alien, it doesn't matter) approaches her beloved Kanata in a remotely romantic way, she emits a black aura and her eyes glow: it's your cue to get away. In such a state she is capable of feats like lifting trees & breaking concrete walls. She's not evil, just [[ClingyJealousGirl clingy]].
* Subverted in ''Manga/SamuraiDeeperKyo'': prior to his [[TimeToUnlockMoreTruePotential further training]] under his master Muramasa, Onime no Kyo was in fact ''weaker'' than Mibu Kyoshiro, who was merely [[ObfuscatingStupidity feigning weakness]] to complete the facade of a harmless medicine peddler.
* Moka's "super-vampire" side in ''Manga/RosarioToVampire''. Super-Vampire Moka speaks to her normal self through her Power Limiter, giving her guidance that she needs. This one isn't evil so much as very emotionally cold, though.
** Though recent chapters have revealed that Inner Moka is the true personality of the one body and the Outer Moka was created [[spoiler: when Moka's powers were sealed by her mother's Rosario so she could go in to hiding. Outer Moka's personality is actually based on her mother Akasha's personality.]]
** Tsukune's ghoul transformation is much closer to the trope. He requires a power limiter like Moka to keep it under control, but unlike Moka, he's a complete monster without it, and only monster of a similar/higher level to Inner Moka stands a chance against him, unless he ''really'' cares about them like his [[TrueCompanions friends]].
*** As of Chapter 41 it seems he's at great risk of becoming [[spoiler: a second [[SealedEvilInACan Alucard.]]]]
* In ''Anime/HeroicAge'', the giant mech-like warriors of the Heroic Tribe, called the Nodos, can eventually let out a Super-Powered Evil Side when two fight together - whether against each other, or side by side - called Mental Chaos, when they enter a pure blind berserker rage. Considering a single Nodos can sometimes destroy a whole planet on its own at its normal levels of power, a Nodos in Mental Chaos is a frightening thing indeed. In Bellcross, the Nodos that serves the human Age, Mental Chaos is shown by his skin and "armor" turning dark gray, almost black, and a set of blue spheres implanted in his body begins to glow bright red. And he roars a lot. Then he begins ''leveling whatever galaxy he's in at that moment, before moving on to another area''.
* Guts, the protagonist of ''{{Manga/Berserk}}'', is known to slip into this state during particularly tense moments.
** [[spoiler:In the manga, this becomes personified by The Beast, a feral lupine creature formed from the considerable amount of rage at the Godhand (and Griffith in particular) and other negative emotions that Guts suffers from after the Eclipse. When Guts is under The Beast's influence, he becomes a danger to everyone around him, even the people he loves -- at one point in the manga, [[NearRapeExperience he almost rapes Casca while under its influence.]] Later on, he acquires the Berserker Armor, an extremely dangerous cursed Dwarven artifact that blinds its user to pain and limitations and causes them to see everything as a threat. It also becomes a kind of physical conduit for The Beast.]]
* In the h-anime ''Makai Tenshi Jibril'' (Translated title: ''Jiburiru - The Devil Angel''), {{Meganekko}}-with-a-crush Meimi is given the sadistic MagicalGirl persona of Misty May, the "Devil" counterpart to the heroine Rika (St. Jibril/Jiburiru).
** Closer to the trope definition would be Rika's evil form in the sequel, or Hikari's Black Aries form in the third game.
* This happened in ''Manga/{{Guyver}}'' once, but it was a doozy. [[spoiler:After his father was turned into an Enzyme Zoanoid and ripped out Sho's brain, the Guyver itself took over Sho and killed his father. Let's just say that when he found out, he didn't take it well.]]
** Though this wasn't so much the Guyver being evil, as obeying its Prime Directive of wearer-preservation.
* In ''Manga/DGrayMan'', Allen's [[EmpathicWeapon Innocence]] seems to have a mind of its own and tends to upgrade itself when Allen gets particularly angry or emotional. It also can control Allen when he's unconscious, and it tends to be very vicious. Then again, it's only dangerous to [[TheHeartless Akuma]].
** Also Arystar Krory, although he has less of a Super-Powered Evil Side than a Super-Powered DeadpanSnarker badass Side.
** There's also the Noah, although they're [[AffablyEvil (affably) evil]] to begin with.
** Allen, with the Fourteenth Noah [[spoiler: who is now making himself heard in conversation, if only to mess with ''the Millennium Earl's'' head.]] The Fourteenth hasn't been seen in actual combat yet, so "superpowered" may still be in question (yeah, right), but [[spoiler:his brief awakening in Allen is enough to terrify a Level 4 akuma and his ability to make Allen display a truly nasty SlasherSmile]] definitely hints at the evil part.
*** In the most recent chapters, [[spoiler:after Kanda stabs Allen and awakens his Noah side,]] there are clear hints that the Fourteenth is ''terrifyingly'' powerful, even by Noah standards. Remember, [[spoiler: this is the guy who apparently ''by himself'' managed to kill off nearly all the previous incarnations of the Noahs and severely injure the Millennium Earl several decades ago]], to wit his laughter after having ''just woken up'' is mistaken for a minor earthquake.
* Son Goku from ''Manga/{{Saiyuki}}''. His 'evil side', the Seiten Taisei, is akin to a heretical chaos god and nearly overthrew the Heavens, goes on an UnstoppableRage whenever unleashed, and usually ends up trashing both the enemy, AND his teammates by the time he's finally stopped. The only thing that keeps him in check is the crown he wears which serves as a RestrainingBolt.
** Cho Hakkai's youkai form would normally just be a SuperMode, but when he changes into it he risks slipping into this due the Minus Wave that is sending youkai berserk. (And consequently, he doesn't pull it out unless the situation is [[GodzillaThreshold beyond dire]] and it's time to set his usual [[StepfordSmiler nice-guy facade]] aside, meaning that even without the Minus Wave there's going to be blood on the walls when he's finished.)
* ''Manga/GreenWorldz'': Akira, the survivor most of the story has focused on so far, has a darker personality hidden within him that tends to come out when he's at a crossroads and pushes him to survive and adapt to their post-apocalyptic world, even if doing so sometimes requires him to do unethical things.
* In ''Manga/SoulEater'':
** [[spoiler:Soul Eater]] is infected by some of Medusa's black blood, which manifests itself as a devil living inside his head [[DealWithTheDevil offering him power in return for giving in to the insanity]]. On the one occasion [[spoiler:he and Maka]] give into it in order to stand a chance against TheDragon, the trope is almost fulfilled to a tee... Except it's not so much a "Super-Powered Evil Side" as a "NighInvulnerable giggling lunatic side who catches TheDragon completely off-guard". [[spoiler:They ''barely'' make it back to sanity, which the devil seems to consider only a temporary setback.]]
** While not anywhere as drastic a change as the above, Stein's tactic against Medusa, of giving into his own madness, could also be seen as this. Though this side is not so much 'hidden' as it is what Stein would ''be'' if he didn't hold himself back through fear. He also seems able to control it frighteningly well, if Spirit's comments at the time are anything to go by.
* Koyori in ''Anime/NurseWitchKomugi'' has a literal evil MagicalGirl SplitPersonality that she is completely unaware of.
* Lina from ''Manga/{{Slayers}}'' when she's [[spoiler:possessed by the being that accidentally created the universe and was presumed to be ready to undo it just as willingly. However, it is instantly subverted as it chastises the villain that made Lina fall to it and unmakes only him and all his plans. Her actual motivations [[BlueAndOrangeMorality are stated to be simply alien to our moral scale]].]]
* The "berserker spirits" aka The Dragons from ''Manga/IkkiTousen''. So far, we have four dragon holders: Hakufu, Ryuubi, Sousou, and [[spoiler:Ryoumou]]
* Eren from ''Manga/AttackOnTitan'' can become a Titan whenever he bites his hand. However, since the power of a Titan isn't easy to control (most of them are mindless ravaging beasts, after all), this tends to make him more ChaoticNeutral than ChaoticEvil like the regular Titans who eat people ForTheEvulz.
* ''Anime/SonicX'': Absorbing the energy of a factory's worth of fake Chaos Emeralds coupled with seeing his friends tortured unleashed [[http://uk.youtube.com/watch?v=XtvplkXKSaY Dark Sonic]] for the first time in animated continuity. Complete with white eyes and navy-dark energy all over his body, plus the ability to tear anything that pisses him off to shreds.
* The main character of ''Manga/SixSixSixSatan'' is actually the container of Satan himself along with nine other demons that have the ability to possess people. There are also ten angels, none of which are evil or trying to take over but some are incredibly vain and judgmental.
* While not necessarily "evil," a mechanical version of this can be found within ''Anime/MobileSuitGundamWing'', specifically in the form of the Zero System, a computer system in the Wing Zero which interfaces with the pilot's brain, enhancing his reaction time and aggressiveness, and allowing him to process tactical data with superhuman speed and efficiency... with a fun little side effect of driving the pilot temporarily AxCrazy. Given that they're still inside a giant, city-killing death machine with all their piloting skills boosted, results are predictably messy.
** The Zero System ''can'' be used safely: the pilot must keep a clear head and not be conflicted in his thoughts towards the battle. In this case the pilot then gains all the benefits without the insanity. Both Heero and Zechs reach this point in the end - and, in fact, Heero eventually becomes so relaxed about the obligatory in-cockpit MindRape that he starts offering it to his fellow pilots as ''therapy''. Astonishingly, [[EpiphanyTherapy it works]].
** ''Anime/MobileSuitGundam00'' also has fun with this - Allelujah Haptism has a SplitPersonality: Hallelujiah, a blood-thirsty "warrior" half who is more skilled than any other pilot in Celestial Being.
*** Then subverted with [[spoiler:The "Ultimate Soldier", aka [[FanNickname H/Allelujah or Doublelujah]], who's an even ''better'' pilot and integrates the best parts of both personalities, including Allelujah's morals.]]
** In the [[Anime/Gundam00AWakeningOftheTrailblazer Gundam 00 movie]] his mech, the Harute, gets one of its own called Marute.
* Then there's the [[Anime/MobileSuitGundamUnicorn Unicorn Gundam.]] Normally a high performance mobile suit with generally above average statistics but nothing of any particularly remarkable quality, when the pilot and it come into contact with a Newtype enemy and the pilot feels a strong enough emotional pull (usually anger), the Gundam feeds off of it and transforms into the eponymous Unicorn Gundam, now in its "NT-D" (Newtype Destroyer) Mode. Its speed ramps up significantly, its strength seems to increase, it gains new abilities related to its psycoframe, and worst of all the suit's AI will stop at nothing short of a manual override or a HeroicRROD to kill any Newtype in weapon range. This is entirely not good for anyone who happens to be facing the thing down, as it generally goes from on an even footing or slightly underperforming the enemy to stomping their face in on a [[CurbStompBattle one-sided epic beating.]]
** After falling victim to this once or twice, Banagher learns how to consciously activate the NT-D system and override its AI, leaving him in complete control of the suit.
* In ''Anime/MobileSuitGundamSEED'', Andrew Waltfeld seemed to likened SEED Mode to berserker rages of the Vikings. While it's not an actual Super-Powered Evil Side, activating SEED Mode while enraged is certainly a glorious mess.
* Dark Schneider/Lucien in ''Manga/{{Bastard}}''. Tiny, fifteen year old boy turns into the infamous eponymous bastard, the all-powerful Exploding Wizard. Then subverted since Darsh does a lot of dorky things outside of battle and seems much more like a JerkWithAHeartOfGold than anything else, with some people often remarking that compared to the Dark Schneider of fifteen years ago, this one is practically a ''saint''.
* In ''Manga/{{Saikano}}'', Chise's personality while in [[PersonofMassDestruction the Ultimate Weapon form]] could be psychotically vindictive, threatening on multiple occasions to utterly eradicate anyone who got in her way or made her mad, be it friend or foe... and that she could do so with ridiculous ease made her even more horrifying.
* In ''Manga/YuYuHakusho'':
** Parodied when Yusuke [[spoiler:dies, and it is revealed that he is in fact part demon. Said demon blood kicks in and he comes BackFromTheDead, with his demonic powers lending him a considerable increase in strength.]] He then decides to have a little fun at the expense of some alarmist commandos who wanted to take him out.
-->'''Yusuke:''' For what I desire is ending the world and everyone in it. For I am [[spoiler:the mighty Mazoku, Lord of Evil! And now, after hibernating for a thousand years I will finally reveal my true form!]] AHAHAHAHAHAHAHAHAHA... psych!! Damn, you guys are gullible!
** Late in his fight with Sensui, [[spoiler:the trope is played straight, as while he still isn't quite able to overpower him, his demonic ancestor Raizen takes control of his body and uses it 'better,' defeating Sensui easily and killing him, which Yusuke is not cool with. Mostly because he wanted to kill Sensui himself...]]
** Sensui himself is an inversion of this trope. Of [[spoiler:his seven personalities, the strongest one is Shinobu, the original one, and the only one to remain pure and innocent. His Kazuya personality, by far the most violent and sadistic, is the weakest personality shown.]]
** Kurama displays a variant on this trope in the Dark Tournament when [[spoiler: his opponent tries to reverse his aging to make him a baby, but goes too far and reverts him to his previous incarnation as a powerful demon bandit.]]
* Mayo Kagura from ''LightNovel/MaiHimeDestiny''. In a series where everyone has {{psychic powers}}, it's hard to stand out when you have boring ol' telekinesis... unless you have a Super-Powered Evil Side that can ''uproot trees and use them as weapons''.
* Ryo Takatsuki from ''Manga/ProjectARMS''. His [[RedRightHand right arm]] is a nanite-based entity known as the Jabberwock. Get him ticked off enough, and the Jabberwock spreads over and takes control of his entire body. Though more really, really angry rather than outright evil, this doesn't stop Jabberwock from doing such feats as tearing apart a helicopter division, numerous other ARMS, emitting ''fire'', and much, much more, [[spoiler: said much, much more means he makes ''anti-matter'' on a whim later on in the manga. Oh yeah, and it evolves too.]]
* In ''VisualNovel/KamigamiNoAsobi'', [[spoiler: [[Myth/NorseMythology Baldr]], the God of Light]] has one, as the [[WalkingWasteland God of Destruction]]. [[spoiler: And Loki, who loves him, will have to kill him to prevent his evil side from destroying the world]].
* In ''Manga/OmamoriHimari'', [[spoiler:all demons, including Himari, can fall prey to their instincts or desires and become savage beasts. In Himari's case, she turns into a nigh unstoppable juggernaut-but, like any other demon, she runs the risk of not being able to return to normal.]] It's explicitly stated that in this situation, they ''will'' be exterminated.
* As of recent events in ''Manga/MahouSenseiNegima'', it seems that [[spoiler:the "Encroachment of [[BlackMagic Magia Erebea]]" is causing Negi to develop one of these.]]
** Played with in that when he learns that [[spoiler: the Super-Powered Evil Side is a product of the Magia Erebea turning him into a demon and that there's no known way to stop it]], rather than decide he'll figure out a way to seal it away permanently, he ''instantly, without hesitation'', decides to get the whole [[spoiler: demonic conversion process]] over with right now and get it out of the way.
** Technically [[spoiler: he agreed without fully understanding how it worked, and Eva just [[SinkOrSwimMentor kickstarted the process.]] Given that the alternative is well, the same thing only over a longer time period, and that the point of the conversion is to get the Super-Powered Evil Side under control, it was really the only viable option anyway.]]
** More like a Super-Powered DarkIsNotEvil Side, really.
* Urd of ''Manga/AhMyGoddess'' (at least in the anime).
* Pikachu in the ''Anime/{{Pokemon}}'' anime practically turned into a demon when he was [[spoiler:possessed by Groudon.]]
* In ''Manga/AirGear'' one of the strongest members of the protagonist's [[FiveManBand team]] has a split personality. Although Agito isn't exactly evil, [[AntiHero his aggressive, bloodthirsty behaviour]] and great skill at the series' [[SeriousBusiness title sport]] make him this to Akito, one of the gentlest characters in the series. Additionally, [[spoiler:later on Agito/Akito discovers he has a third personality named Lind who embodies this trope. He's the polar opposite of Akito and is implied to be much better at Air Gear than Agito. Although his intentions are still largely unknown, Agito himself warns the protagonist that Lind will probably end up becoming the main personality and betraying him.]]
* ''Manga/{{Change 123}}'' demonstrates why, in the real world, this is less of a cool new power and more of a deadly serious problem; you don't want your high-school girlfriend to snap and try to kill someone on your behalf because they said nasty things about you...[[spoiler:or to try to kill you because you tried to stop her from killing that person.]]
* ''Franchise/{{Digimon}}'' has a few examples of this:
** In ''[[Anime/DigimonAdventure Adventure]]'', Taichi tries to force Agumon to evolve to perfect, causing the creation of [=SkullGreymon=].
** ''Anime/DigimonTamers'' has Megidramon formed when Takato watches Leomon die, who is so powerful the Digital World starts ''collapsing''.
** ''Anime/DigimonFrontier'' [[spoiler: Koichi]] spends about half the series as his SuperPoweredEvilSide Duskmon/Velgemon before it's revealed that he's [[spoiler: Koji's brother]] and gets his Digispirits purified to Loweemon/[=JagerLoweemon=]. He never seems quite as powerful after returning from the TheDarkSide.
** In ''Anime/DigimonSavers'', Marcus' emotion get the better of him, too, forcing [=ShineGreymon=] to enter ruin mode.
** ''Anime/DigimonXrosWars'' has two examples- [=DarkVolumon=] for [[spoiler: Ballistamon]] and the Whisper virus for [[spoiler: Apollomon]]. Surprisingly enough, Shoutmon averted this by having no "evil" powered side.
* In ''Manga/ViolinistOfHameln'', Hamel's [[spoiler:mazoku blood]] gives him a Super-Powered Evil Side that, however, is not usually activated by rage or being near death, as it usually the case, but instead takes over whenever he cannot carry on anymore and is close to HeroicBSOD. It comes with demonic physical changes, such as horns and wings, is powerful enough to easily devastate whole cities, indiscriminately murderous and completely uncontrollable [[spoiler: until the final battle, when Hamel managed to stay in control despite the full-body mazoku transformation, because that time he fought for his friends and love and only transformed because the BigBad's power level was high enough to warrant it.]]
* Tohma in ''Manga/MagicalRecordLyricalNanohaForce'' has his Black Knight form. When it comes out, he gains a HealingFactor, powerful magic, and is capable of performing a Zero Effect, which greatly drains the energies of anyone and anything in a wide area. Unfortunately, he loses over half his consciousness in this form, replacing it with an insatiable need to kill.
* ''Manga/DNAngel'':
** Satoshi has [[spoiler: Krad, one half of an extremely powerful artwork who likes killing people,]] living in his head.
** Daisuke has Dark [[spoiler: , the other half of the same artwork]] living in HIS head, although Dark's more mischievous than evil.
** Krad's fandom nickname: Homicidal Blonde.
* [[EvilGenius Brain]] from ''Manga/FairyTail'' has [[AxCrazy Zero]], who is twice as strong as him and far more adept in combat, being credited as the ''true'' master of Oracion Seis. He's so dangerous that Brain sealed him away [[spoiler:with special keys that link all the members of the Oracion Seis, and he emerges when the Oracion Seis are all defeated to finish what they started.]]
** Also Rogue, whose magic causes the darkness in his heart to manifest as his shadow, tempting him to do evil and even possessing him once to give him a power up and try to force him to kill.
** [[spoiler: Natsu, as it turns out, is the true identity of E.N.D., the most powerful demon ever created by the BigBad, Zeref. While not much else is known about him, its indicated that even the dragon Acnologia is leery of him, which no doubts says a lot about E.N.D.'s power level.]]
* ''Franchise/SailorMoon'':
** Hotaru Tomoe has ''two'' other sides. Sailor Saturn and Mistress 9, who nearly destroyed the world. Hotaru also subverts this trope. Sailor Saturn's breed of destruction is basically a cosmic ResetButton - albeit one that's only marginally better than outright annihilation. Mistress 9, on the other hand, is desperately weak; the Deathbusters' scheme in the second half of the season boiled down to saving her before she (and Hotaru) curled up and died.
** Also Chibi-usa, who had one as well when she was brainwashed by the Wiseman, known as the Black Lady.
* [[http://www.youtube.com/watch?v=Zf0uzEhbg88 This short cartoon]] about an anthro clione, whose SES is based on his real-life counterpart's mouth. [[http://www.youtube.com/watch?v=Kc50vlH6DJ8&NR=1 The sequel]] stars a female version with a dash of {{Tsundere}}.
* When Manga/{{Yaiba}} loses control of the Raijin Sword he turns into a [[ShockAndAwe lightning-blasting]], destructive avatar of the God of Thunder.
* In the series ''LightNovel/ACertainMagicalIndex'', the main character Touma was shown to [[spoiler:have an actual sentient being inside of him that appeared after having his arm cut off. The guy who cut off said arm had an OhCrap moment when he realised that his power paled in comparison even though he reached the point of being higher than God. (This is a given because Touma's last name Kamijou can be translated several ways, one being "Invisible Demon".)]]
* ''Manga/OnePiece'' has Chopper, a shapeshifter who normally has three forms available. When he eats a Rumble Ball, he gets access to four more forms for three minutes. If he eats another before the cooldown wears off, he gets three more minutes, but the shapeshifting is uncontrollable. If he eats a ''third'', he morphs into a giant monster that's incredibly powerful, incredibly resilient, and absolutely uncontrollable. In its first appearance, he [[CurbStompBattle one-shotted]] an enemy who had been beating him handily a moment before, then smashed through a castle wall and went on a rampage, destroying a dozen rooms before Franky managed to throw him into the ocean.
** As of Chapter 645 [[spoiler: Chopper has now mastered his monster form]].
** In the kingdom of Rommel, there was phenomenon where it seemed as if the wind itself was cutting people. Eventually, a Marine warship was sent out to investigate, and the culprit was found to be a man by the name of Hakuba. Even to this day, he still hasn't been caught, but he still appears in towns where a certain pirate resides. The pirate in question? [[spoiler:Cavendish. In fact, Hakuba is the one who went out to sea to become the pirate named Cavendish.]]
* Piss off the softspoken, easygoing and always smiling Wolfgang Grimmer, from Creator/NaokiUrasawa's ''Manga/{{Monster}}'', and you'll have to deal with "The Magnificent Steiner". [[NoHoldsBarredBeatdown Carnage ensues]] - though it's never directly shown.
* The main character of ''Manga/IkkiTousen'', Sonsaku Hakufu, is a token IdiotHero with enough fighting skill to beat the crap out of a school attended only by martial artists and assorted thugs. But sometimes the enemy is just above her [[PowerLevels level]] and she finds herself beaten almost to death: vision blurs, strengh fades... [[OhCrap Congratulations!]] You've awakened "the power of the dragon" and the last thing you are likely to see is her [[FetishFuel raptured expression]], while she [[NightmareFuel strangles you to death]] or is about to stab you with a sword.
** To be honest, everyone possessed by a dragon soul behaves this way... even if [[BewareTheNiceOnes not a fighter]] -- the biggest example is Gentoku Ryuubi, a ButtMonkey CuteClumsyGirl who happens to possess a Dragon Soul ''even more powerful than Hakufu's'', and when taken over by it she becomes a totally savage PersonOfMassDestruction.
* Akira Fudou and Amon from ''Manga/{{Devilman}}'' may be the oldest example in the history of manga. And also an UnbuiltTrope, as the manga shows that having one wouldn't just conveniently let you send it out on enemy too strong for you to take - taking Amon's powers changes Akira from meek and gentle boy into complete BloodKnight and that even without letting Amon out. Amon however only breaks free in a SpinOff manga ''AMON'', and an OVA of the same title. In the anime Amon '''[[spoiler: eats a little girl alive]]''' and in the manga he is maybe just a bitter AntiHero, but still destroys several ''countries'', just by [[WalkingWasteland passing through them]].
* ''LightNovel/TrinityBlood'': Father Abel Nightroad [[ObfuscatingStupidity only looks like a bumbling idiot]] most of the time -- in reality, he's an extremely powerful and extremely dangerous Crusnik, a super-vampire that preys on regular vampires. He voluntarily limits his power to 80% activated, at most, though, although he does suffer from SanitySlippage at that point. [[spoiler: His [[EvilTwin brother]], Cain, [[WithGreatPowerComesGreatInsanity was driven to insanity by fully-activating his power]], so yeah, that voluntary PowerLimiter is actually a good thing.]]
* Kagura, the adorable, profane, sukonbu-chewing, nose-picking heroine from ''{{Manga/Gintama}}'' goes from [[http://i195.photobucket.com/albums/z33/krnlilangel94/Gintama/Snapshot2008-06-2115-55-18.png this]] to [[http://desmond.imageshack.us/Himg233/scaled.php?server=233&filename=kagurakillermode.png&res=landing this]] when the self-imposed chains on her Yato blood get broken. She stops fighting to win and instead fights to kill with a savagery that scares her.
* The protagonist of ''Manga/TheThreeEyedOne'', Hosuke Sharaku, is a tiny, wimpy, Charlie Brown-esque boy who turns into an immensely powerful, larger, psychic supervillain when the bandage on his forehead is removed, revealing his third eye.
* Double-subverted (at least) in ''Super Taboo'' with [[NiceGuy Yuu]] turning into [[GoodEyesEvilEyes "Instinct Yuu,"]] which is less OmnicidalManiac and more the personification of AllGirlsWantBadBoys that's initially ''desired'' by his [[IncestIsRelative mother and sister]] since that side awakens whenever he's sexually aroused [[WhatDidIDoLastNight (minus everyone being drunk on Christmas)]] and implied to be [[InTheBlood inherited from his father,]] whose [[CompellingVoice voice is even mesmerizing enough for Up To Eleven Phone Sex with his wife.]] Other than the confusing blackouts and [[MyGodWhatHaveIDone reactions to sleeping with various women]] it/he's harmless until [[TookALevelInJerkass getting too rough with his sister,]] requiring a BattleInTheCenterOfTheMind where Reason and Instinct (previously just a running gag where Instinct curbstomps Reason in cartoon-form ex. Barney-like dragon eating a knight) are personified as a BettyAndVeronica that he has to choose between despite EvilIsSexy. He finally chooses to be with Reason and rewarded with one last shot at his mom as himself (who's somehow a virgin) before being more steady with his [[BrotherSisterIncest sister as a happily ever after.]]
* In ''Anime/SteelAngelKurumi'', at least the anime version, it's revealed that Kurumi's Angel Heart Mk. II has both an angel ''and'' a demon in it. Thanks to Nakahito commanding Kurumi not to hurt people, Kurumi finds herself helpless during fights because she doesn't want to hurt anyone, especially her fellow Steel Angel sisters. The demon side manifests soon after, BlankWhiteEyes, grim demeanor and the ability to punch holes into walls ''from a distance''. When Nakahito's kidnapped in an attempt to find out why his power makes Kurumi stronger, she starts to freak out and slip farther and farther into this power until everyone is forced to use a last-ditch weapon to kill her. Thankfully, Nakahito's able to break through to her and TrueLovesKiss ends up purifying her heart.
* In ''{{Franchise/Anpanman}}'', Rollpanna is already a superheroine, but with two hearts: a good one and an evil one. Being under the influence of Baikinman or being near Anpanman triggers her evil heart, which powers her up even more, but she can snap out of it when by her younger siblings, Melonpanna and Creampanda. Sometimes, Baikinman uses dirty tricks to completely remove her good side, turning her into Black Rollpanna, a ruthless fighter that is even more powerful than when she has both hearts, and nothing stops her, not even her siblings, until both hearts are together. For these reasons, she prefers to wander the earth alone, in fear of her evil heart being triggered.
* ''LightNovel/VampireHunterD'': {{Dhampyr}}s (human/vampire hybrids) can 'vamp-out' under physical and/or emotional stress and start exhibit Noble-like traits such as drinking blood, etc. Given how powerful D is when he's ''trying'' to act mostly human, when his Noble side emerges, expect plenty of OhCrap moments and [[CurbstompBattle Curbstomp Battles]].
* ''LightNovel/BeyondTheBoundary'': Akihito loses control of his [[HalfHumanHybrid youmu side]] after sustaining severe injuries. He is [[PersonOfMassDestruction immensely powerful]] in this state, requiring 3 people just to contain him. One stray fireball creates an enormous explosion when it hits a nearby mountain and he levels his surrounding area.
* ''Anime/CodeGeass'': Lelouch's ThenLetMeBeEvil moment at the end of the second season where he [[spoiler: Geasses all of the army guys to become his personal slaves]] showing if he was to be evil he would be a complete monster [[spoiler: Completed by him taking over the world]]
* In ''Manga/{{X 1999}}'', [[spoiler: BigGood Hinoto is shown to have one of these, who wants to unleash TheEndOfTheWorldAsWeKnowIt to become the only DreamWeaver.]] When the manga was given a NoEnding, [[spoiler: her Dark Self [[SplitPersonalityTakeover has completely taken over her]].]] This is dealt differently in the TV series, [[spoiler: where Hinoto goes through an HeroicSuicide to stop said Dark Self.]]
* ''Franchise/KagerouProject'': Konoha, SuperPoweredAlterEgo for IllBoy Haruka Kokonose, is a downplayed example. While he is in fact a very caring individual - like the real Haruka - it is noted by other characters that despite noble intentions, [[SuperStrength he uses]] [[FlashStep his powers]] to solve problems with violence and destruction. [[spoiler:Not to mention that he's a DemonicPossession away from being used to massacre every other main character, [[GroundhogDayLoop and does so every few thousand years]]]].
* Wretched Egg is this to [[spoiler:Shiro]] in ''Manga/DeadmanWonderland''. [[spoiler:Shiro]] is a nice teenager while [[TheDreaded Wretched Egg]] is super-powered and incredibly murderous. [[spoiler:Subverted near the end when Shiro reveals that both personas were a lie. She's in control either way and is really a DeathSeeker.]]
* Mob's ???% form in ''Manga/MobPsycho100'' comes out when Mob falls unconscious, and is not only far more powerful than Mob at even 100%, but is also far less restrained in how it uses that power - though, as a defense mechanism, it doesn't seem actively malicious.
* In ''Manga/Brave10'', it turns out [[spoiler:the sweet naive {{miko}} Isanami]] is the vessel for the DestroyerDeity [[spoiler:Izanami]].
* Ryner Lute from Anime/TheLegendOfTheLegendaryHeroes is lazy but if you hurt one of his friends, you will see why Alpha Stigmas are feared: an evil God of Destruction personality with overwhelming powers will just disintegrate you.
-->'''Ryner Lute:''' First comes destruction. I bring forth nothing. I bless nothing. I save nothing. I just erase. Completely

[[folder:Comic Books]]
* In the Creator/AlanMoore Retelling of the comic ''Marvelman'', ''ComicBook/{{Miracleman}}'', Kid Miracleman is the only survivor of a nuclear blast (he thinks) and stays in his superpowered form for years. In this form, but using his civilian name of Johnny Bates, he grows up. His moral code begins to erode because he is the most powerful man on earth and he has no one to tell him what to do. When Miracleman confronts him years later, he is the CEO of a computer company and a rather nasty piece of work. They fight, and he is forced to change back into a normal human ''child'' (His other self didn't age for ''years'' while in stasis) and left at an orphanage. There he is constantly bullied by other orphans, having to carry the dreadful knowledge that he could become more powerful than any of them, but he dare not because KM would start killing people. Then he is pinned one day, and some of the boys attempt to gang rape him, and this pushes him past the breaking point. The resulting awakening of KM results in the slaughter of the boys and a significant number of the population of London. Miracleman is forced to make him transform back into a human and end his life with a NeckSnap.
** In an [[StoryWithinAStory apocryphal story called "The Rascal Prince"]], a book read by followers of Johnny Bates who think he was a tragic victim tells a tale two ways: The revisionist version that depicts KM's meeting with an older woman as a flirty chaste romance, and as the RealLife version depicting [[NightmareFuel the rape of an unwilling victim]].
* The ComicBook/IncredibleHulk is the canonical super-Hyde. The Hulk, over time, has been softened down from "evil" to "pure id". Not that that stops him from racking up the damage bill every time he shows up.
** Banner does have the Devil Hulk personality inside him, which is pure evil.
** As well as [[{{Jerkass}} Gray Hulk]] and [[WhatHaveIDone Guilt Hulk]] -- though Grey Hulk isn't really "evil"; he's another closer to "id".
** Bruce Banner's wife Betty Ross has been transformed into the villainous Harpy. She's currently Red She-Hulk, who's more TheAtoner.
* ''Franchise/XMen'':
** ComicBook/{{Wolverine}} has a tendency to lapse into a "berserker rage" while in close combat. In this state he lashes out with the intensity and aggression of a mindless animal and is even more resistant to psionic attack. Though he loathes it, he acknowledges that it has saved his life countless times. Of course, he uses it so often without negative side effects that the whole "evil side" part is something of an InformedFlaw.
** It's still not clear whether Dark Phoenix is ''Comicbook/JeanGrey'''s Super-Powered Evil Side or a variation on GrandTheftMe. (Whether Jean actually ''became'' Phoenix (and then Dark Phoenix) or was merely ''replaced'' by the Phoenix Force is in an almost constant state of {{retcon}}, so the confusion is quite understandable.) However, one thing remains the same: if you see her [[EvilCostumeSwitch green costume turn red]], you want to be in the next galaxy over. (That's NotHyperbole; she's responsible for the eradication of a whole solar system.)
** Angel has Archangel, the persona he developed after being experimented on by Apocalypse. Warren usually has wings and average healing powers. Archangel has razor sharp, retractable wings that launch out metal feathers that are dipped in his natural poison. X-Force had to call upon Archangel more than a few times, though he has since been extinguished, and Angel now possesses angelic metal wings.
* The ComicBook/NewMutants [[ComicBook/IllyanaRasputin Magik]], way back when, was partially transformed into a demon by Belasco. Her "Darkchylde" side is intelligent but malicious, though almost powerless on Earth, where her magic doesn't work very well. In the end it took over her and nearly ended the world in a major Crossover Event.
** Legion from the same series was first introduced with a Super-Powered Evil Side in Jack Wayne, as well as a Super-Powered Jerkass Side (the pyrotic Cyndi). He usually has one or more evil personalities, except when they are temporarily merged.
** His father Charles Xavier also sometimes suffers from this trope. First, in a crossover mini-series with the Micronauts there was the Entity, a personification of his dark side. Later there was the supremely powerful Onslaught, who also contained elements of Magneto's evil side. Then there is Cassandra Nova, who combines this trope with elements of the evil twin and alien invader.
* J'onn J'onzz, the ComicBook/MartianManhunter, has a [[WeaksauceWeakness fear of fire]] for good reason. When he loses his fear of fire? He unleashes Fernus, the last Burning Martian who beat the entire ComicBook/JusticeLeagueOfAmerica at once and Batman needed to call ComicBook/PlasticMan in to help.
** [[ItMakesSenseInContext Yes.]] ''[[ItMakesSenseInContext That]]'' [[BewareTheSillyOnes Plastic Man.]]
* Super Sonic in the British ''ComicBook/SonicTheComic'' comic series. In that comic's canon, the Chaos Emeralds are full of pure evil (as energy), rather than their neutral alignment as confirmed as canon by ''Sonic Adventure''. Super Sonic came about by overexposure to the Chaos Emeralds, and as such... he's insane, and evil, sadistic, psychopathic... and equipped with the power of the Chaos Emeralds. When he split from Sonic and lost his powers he mellowed out, but returned to form when he got them back. The Archie comics did a homage to this in one issue, although in that canon there's generally no personality difference between Sonic and Super Sonic, Doctor Robotnik is also this to his former self [[FriendToAllLivingThings Dr Ovi Kintobor]], due to exposure to raw evil Chaos Energy.
* ComicBook/TheSentry and the Void, from Marvel Comics, are this trope taken to its extreme. They manifested as alter-egos of a single person, representing the good and dark sides of humanity, respectively. The Sentry is a superhero and the Void is a supervillain, and in a slight variation on this trope, the Void is exactly as powerful as the Sentry, and occasionally kills someone for every person the Sentry saves.
** It was later revealed that [[spoiler: the Void exists because before becoming the Sentry, Bob Reynolds was a junkie who broke into a research facility looking for crystal meth and ended up drinking a potion that gave him the powers of the Sentry. He became addicted to that potion and the rush of being an admired and respected superhero, but deep down he was still a selfish, murdering junkie -- and this expressed itself through the Void.]]
** And ''later'' it was revealed that the Void [[spoiler:was in fact the Angel of Death]]. ComicBook/TheSentry is [[MultipleChoicePast kind of a mess]].
* ''ComicBook/RisingStars'':
** Stephanie Maas/Critical Maas; The only normal in a town full of superheroes actually just shunted her super powers (including flight, strength, and creepy-puppetmaster mind control) into her secondary, psychopath personality.
** Incidentally, Critical Maas is undoubtedly the inspiration for ''Heroes''' Jessica/Niki, right down to [[spoiler:her history of abuse by her father]] and her penchant for calling her 'weaker' half 'little mouse'.
* Jackie Estacado in ''ComicBook/TheDarkness'' also fits this, and likes it during the early parts of the series, as it gives him more unique ways to kill people.
* ''SpiderMan'':
** Mr. Negative, a new [[Comicbook/SpiderMan Spider-Man]] villain, takes this to a whole new level. [[spoiler: He was born when a synthetic drug split a man's personality in two - the pure good side became philanthropist Martin Li, while the pure evil side became Mr. Negative.]] Both fight with each other in an interesting way - Negative likes to corrupt all [[spoiler: Li's]] good deeds, while [[spoiler: Li]] helps people that suffer because of Negative.
** Curt Connors and Lizard are often portrayed this way [[spoiler: However, there's a RetCon which reveals that Connors was always in control of Lizard and let him out when life was too hard for him. He just keeps telling himself it's not true.]]
** Though not portrayed this way in the original comics, all subsequent portrayals of the Venom symbiote have made it out to be this, with even the comic book symbiote having been {{RetCon}}ned into a more malevolent entity.
* Franchise/{{Batman}}:
** In the ComicBook/BatmanRIP storyline, Dr Hurt's mental attacks on Batman unleash a "back-up personality" Bruce had installed in his psyche, known as the "Batman of Zur-En-Arrh", who is essentially Batman without Bruce Wayne, i.e. completely unstoppable, but willing to do things the normal Batman wouldn't dream of to get results (including, it is implied, torture). Once again, more of a "superpowered" (he's still a BadassNormal) Id AntiHero side than truly evil.
** Two-Face is sometimes treated this way, [[BadGuysDoTheDirtyWork being able to do the nasty deeds]] that "good" Harvey Dent can't bring himself to. This is particularly evident in the story [[http://www.youtube.com/watch?v=sKPLopZt6b4&hd=1 "Two of a Kind"]].
** An ''Elseworld'' story called "Batman/Etrigan: A Tragedy", Bruce Wayne is (unknowingly) the host of Etrigan the Demon, who emerges every night to violently battle criminals in Gotham. However, Etrigan is only as restrained as he is because of Bruce's virtue, and in reality, Bruce has been trapped with Etrigan for over a thousand years, pretending to be his own descendant unknown to himself because his servant Alfred (in reality Merlin the wizard), has kept watch over him and constantly changed his identity for all this time out of guilt of dooming him to an eternity as a prison for Etrigan. Bruce attempts to excise Etrigan, but the results are disastrous, resulting in the deaths of Catwoman, Killer Croc, Commissioner Gordon and several police officers, as well as Bruce's fiancee Glenda. Bruce consigns himself to repeating the cycle once more as Etrigans jailer.
* Eclipso has acted as this to various characters in the DC universe. Subverted in one ''ComicBook/BlueBeetle'' comic, where Eclipso invokes this by releasing Jaime's darkest fantasy of ultimate power to serve as her champion against Paco. This backfires when [[spoiler: this turns out to be a [[CrowningMomentOfFunny dentist]], who is easily defeated (Jamie's deepest desire has nothing to do with power, what he wants is a stable career to help support his family).]]
* ComicBook/{{Raven}} of the [[Comicbook/TeenTitans Titans]] has to maintain strict control over her emotions to the point of being TheStoic. If she doesn't, she runs the risk of manifesting the extradimensional demon side of her family tree and becoming DaddysLittleVillain. This is one of the major reasons Raven and Beast Boy have never been able to make a relationship work in the long run despite strong mutual feelings for each other.
* The Golden Age version of the Cheetah, WonderWoman villain, was the violent split personality of a celebrity, Priscilla Rich.
* Star Sapphire, villain and LoveInterest of GreenLantern Hal Jordan, was similar, with Carol Ferris being unaware of what her alter ago was up to.
** The Golden Age Green Lantern also had a villainess who was an otherwise innocent woman's split personality, the first Thorn. Alan Scott would actually end up marrying the Thorn's good side, Rose Forrest, while she was using an assumed name. Unfortunately, the Thorn re-manifested and Rose fled for Alan's sake, and then later had to give up her children to protect them. These children were in fact Obsidian and Jade. Some time later Rose would have another child, Mayflower of the Force of July, but her father was never revealed.
* Astronaut Brice Rogers became the MoonMan after passing through a comet's tail while traveling to the Moon. During the day he was Brice, but exposure to moonlight forced the emergence of his criminal alter ego.
* In pre-Crisis on Infinite Earths continuity, Stacy Macklin appeared for several years in DC's Wonder Woman series. She made her final appearance in World's Finest, inheriting Moonman's powers and developing an alter ego as Lady Lunar.
* Comicbook/{{Etrigan}} serves as this to his host Jason Blood.
* Anti-hero (but firmly one of the good guys) Hellhound in ''ComicBook/AstroCity'''s Dark Ages arc has a huge, colorful demon inside him. When it comes out, well, the demon isn't one of the good guys.
* The third Black Knight Dane Whitman's first squire, Sean Dolan, suffers from this. As himself, he's a normal human [[PluckyGirl Plucky Boy]] and BoisterousBruiser-in-training who looks up to Whitman and wants to be a good sidekick. But when he makes the mistake of drawing Whitman's cursed sword, he turns into the demonic Bloodwraith who is willing to kill good and bad alike, cruelly mocks Whitman and his friends and can (literally!) level small countries. Sean spends much of the time afterwards trying to keep his evil side and addiction to the sword's influence under control and failing miserably.

* ''ComicBook/{{Supergirl}}'':
** In the ''ComicBook/RedDaughterOfKrypton'' story arc, Siobhan Smythe -who usually is the super-villain named Silver Banshee- let her Silver Banshee evil self out during her fight with Supergirl to try to hold her mindless friend back. Despite of her fears, she manages to keep her banshee side under control.
** In ''[[ComicBook/Supergirl1982 Supergirl vol. 2]]'' college professor Barry Metzer built a machine to kick-start his brain and body's evolution; but he developed an evil, ruthless split personality who took over.
* In ''ComicBook/{{Daredevil}}'' and related comics, Mary Walker is a sweet, innocent woman who has two evil personalities, Typhoid Mary and Bloody Mary, who have sole access to their super powers.
* ''ComicBook/DoomPatrol'' has Crazy Jane, a woman with severe Split Personality Disorder, caused by sexual abuse by her father. When the alien Dominators detonated their gene bomb during the "Invasion" event, activating the metagene in thousands of humans, Jane was one of those affected. Jane has 64 different personalities, some good, some bad, and some neutral or inactive (the Jane personality has no powers). Among the evil ones are Black Annis (a violent, psychotic misandrist with blue skin and razorsharp claws and teeth), and "Daddy" (a giant copy of Jane's father made of insects, excrement and puzzle pieces). The Daddy persona was destroyed when Robotman entered Jane's psyche and helped her defeat him.
* In ''ComicBook/TheLeagueOfExtraordinaryGentlemen'', Hyde is this to Jekyll. He points out (true to the source material) that this was not originally the case. Quite the opposite: Jekyll was originally a big strapping fellow while Hyde was rather diminutive. The reason Jekyll is a pale and sickly shadow of his former self while Hyde is a big hulking brute now? [[spoiler:As the Invisible Man's blood starts appearing on Hyde due to the former's death at Hyde's hands]], Hyde explains that without Hyde, Jekyll has no drive, and without Jekyll, Hyde has no ''restraints''.

[[folder:Fan Works]]
* In ''Fanfic/ChildOfTheStorm'', Harry has a dark side that starts appearing after chapter 50. While not strictly another personality, it's certainly another side of him. According to Carol (who's had a look inside his mind), like all the experiences that should have screwed him up have been locked away in a box in his mind, constituting his dark side. It's [[TranquilFury frighteningly cold]], ruthlessly calculating, and while not explicitly more powerful, Carol describes it as TheUnfettered, while others describe it as being frighteningly reminiscent of a young Magneto. In one early appearance, it led to Harry systematically dismantling the entire Ravenclaw Quidditch team in revenge for the bullying/being complicit in the bullying of Luna Lovegood. Later, it resulted in Harry putting an entire HYDRA assault team at his mercy and nearly forcing a PsychicAssistedSuicide after their leader took a child hostage, only being talked down by Jane. Then, a chapter later, it led to him telekinetically ripping Gravemoss' ribcage open and tearing his heart out (not that it had [[HealingFactor any long term effect]]). Unsurprisingly, [[BestFriend Carol]] [[MoralityChain keeps a close watch on him]], as Harry does on himself, being invariably horrified by what he's done when it sinks in.
** Towards the end of the first book, Harry's protection is revealed as a fragment of the Phoenix Force, and the start of ''Ghosts of the Past'' shows that he can tap into it. Considering the already mentioned dark side and that the Phoenix has taken him over to protect him, appearing in the gear of the Dark Phoenix and destroying everything in its way, this is rather worrying - while the Phoenix is broadly benevolent or at least, [[spoiler: Lily, the White Phoenix of the Crown,]] is, the power itself is a) morally neutral, b) incredibly volatile. As a result, Loki's fear is that that the two will combine and turn him into the Dark Phoenix. [[spoiler: This fear turns out to be entirely justified.]]
** Bucky's Winter Soldier persona functions as this. He's still got the same abilities and skills, the Soldier persona is just much more ruthless, focused, and economical.
* In the ''WesternAnimation/JackieChanAdventures'' fic ''FanFic/QueenOfAllOni'', the re-emergence of Jade's Queen of the Shadowkhan persona and her StartOfDarkness that occurs because of it is what kicks off the entire plot.
* In the Death Note fanfic [[http://www.fanfiction.net/s/9644493/1/Zenith-Darkness-Reverie Zenith, Darkness, Reverie]], this is [[spoiler: Kira's]] purpose. [[spoiler: Although the "superpower" in question is Kira's utter lack of morality and the willingness to wield the Death Note. [[BrokenAce Kali is]] arguably the more intelligent/strategically capable personality.]]
* In the ''Fanfic/PonyPOVSeries'', Princess Luna ''nearly'' reverts back into her [[MadGod Nightmare Moon]] form as a last ditch attempt to [[EvilVersusEvil stop Discord]], but manages to snap out of it. It's later revealed that at least some ponies have a similar Super-Powered Evil Side; Rainbow Dash nearly transforms before being calmed down at one point. Unfortunately, [[spoiler: nopony is around to calm [[BewareTheNiceOnes Fluttershy]] down when she snaps and she transforms into the RealityWarping {{Mad God}}dess named Princess Gaia, a WellIntentionedExtremist [[UtopiaJustifiesTheMeans who seeks to turn the world into a utopia]] by [[BrainwashingForTheGreaterGood brainwashing everyone into being happy]] and [[FountainOfYouth turning them into foals because she perceives them as being happier at that age.]]]]
** [[spoiler: It's revealed in "Playtime" that Princess Gaia was simply an illusion hiding her ''real'' Super-Powered Evil Side, the monstrous Nightmare Whisper.]]
** Luna explains the Super-Powered Evil Side thing a bit in "AJ's Dream": it's what happens when a single aspect of an alicorn (or being with a similar power, like a wielder of an Element of Harmony) consumes them and becomes the ''only'' part of them. Nightmare Moon was when Luna's night became the only thing that mattered to her and [[spoiler: Nightmare Whisper was when Fluttershy was consumed by her kindness]]. We're also shown possible Super-Powered Evil Side forms for Applejack (Nightmare Mirror), Rainbow Dash (Nightmare Manacle), and Pinkie Pie (Nightmare Granfalloon), though all of which are AlternateUniverse versions of the mane cast.
** [[spoiler: The final stretch of the Dark World arc introduces Nightmare Eclipse, an alternate-timeline Twilight Sparkle gone Nightmare after being consumed by the desire to make Discord suffer for what he's done, and thus created a GroundhogDayLoop to trap him in, deleting each world and rewinding time each time Discord is defeated so he can suffer some more... and not caring that she's casually deleting/killing millions of innocent ponies each & every time she resets the loop.]]
** [[spoiler: In addition, the end of the Mind Games arc sees Diamond Tiara transform into a Nightmare, but as a result of Discord's psychological manipulation and breaking of her spirit rather than a facet of herself consuming her. Her theme is Discord's brand of chaos, and she earns [[TabletopGame/{{Warhammer 40000}} a certain eight-pointed star symbol]] as her new Cutie Mark.]]
* In the Fanfic/ShadowWars universe, a Nightmare can happen naturally or with the assistance of the [[DarkIsEvil Night]] [[LivingShadow Shadows]], horrible parasitic [[DemonicPossession possessors]] from a dying alternate universe.
* There are a couple among the children of Fanfic/TheEmiyaClan.
** Sakuya inherited part of the Angra Mainyu from her mother. Perhaps because of the diluted bloodline, it manifested itself as a slightly annoying second personality rather than a mad dark mode. The family calls them '''Yin''' and Yang to keep things simple. Yang is a bookish, modest, and generally reserved girl with a small fascination with YuriGenre. '''Yin''' is an openly perverted, conniving, and slightly sadistic YaoiFangirl.
** Haru, [[OurVampiresAreDifferent by virtue of being a vampire]], has his Dead Apostle side. It's more of a berserk mode, but an alternate future version of him, DA!Haru showcases what it could have made him into if he ever let it get out of control.
** Touma's ten years of torture and experimentation before being rescued left him with a cold blooded alter ego called, [[TheDreaded ''The Ghost'']]. It isn't evil, but it has no moral inhibition, wiling to do whatever it takes to protect those he cares for.
** Mana Ryougi has her alternate male personality, MANA, as per her family trait. She hates being told what to do by anyone, including herself, so she mostly ignores him. [[spoiler: Until she has her DespairEventHorizon.]]
* In ''{{FanFic/Heir}}'' by Na'hiel "Tom" [[spoiler: [[Franchise/HarryPotter the horcrux Voldemort]] accidentally made that resides in Harry's scar which has became sentient [[LimaSyndrome and very protective of his host]]]] is this for [[TheKidWithTheLeash Harry]].
* Played with in ''Fanfic/HarryPotterAndTheMethodsOfRationality''. Harry has what he calls a "dark" side, which is extremely good at plotting and seeing through plots... but that's it. Harry, who is familiar with this trope, is ''very'' put out when he discovers that it's no better at magic than him, and thus considers his "dark" side to be defective.
* Played straight in ''Fanfic/AhArchfall''. Even before he had his Archs, Jago was a competent fighter but when things got rough, he could us his dark power side, known as "Papa Jupiter". At his most basic level, Jupiter can boost Jago's fighting power to the point where he can plaster ten grown men. At the full extent of his powers, he is AT LEAST as powerful as either the Almighty One or Lady Hild (possibly more so). Unfortunately at this level of power, he has no problem with killing people, even those he cares about (though he prefers enemies as they tend to fight back). [[spoiler:As the story progresses, its revealed that Jupiter taking over is the only thing that Jago is REALLY afraid of. This is brought to a head during the Deity Games when he faces a mirror that reflects a person's worst fears as sees the result of what a fully unleashed Jupiter can do; he devastates the world, crucifies Lamb and Damascus, beats Lind to death with a rock and uses his knife to murder their infant son. The physic torment this causes is so great that it actually makes the mirror shatter.]]
* In ''FanFic/{{Mirrored}}'' [[spoiler: while stuck in Voldemort's form]] Harry draws on the power of the [[spoiler: horcrux.]] Subverted because while the [[spoiler: horcrux]] gives him a significant boost it is acting in complete accordance with Harry's desires [[spoiler: [[DeathSeeker even the desire for Voldemort's death.]]]]
* In the ''Film/StarTrekIntoDarkness'' fic ''[[http://www.fanfiction.net/s/9344456/1/That-Was-A-Good-Fight That Was A Good Fight]]'' this happens to Kirk as a side-effect of [[spoiler: Khan's blood]].
* In the ''FanFic/TamersForeverSeries'', [[spoiler: Chaos is Takato's Super-Powered Evil Side, and the reason why pushing Takato's BerserkButton is a '''''very''''' bad idea]].
* ''FanFic/ShadowsAwakening'': Jade gains a Shadowkhan form that she can [[HenshinHero switch in and out of]], which gives her an edge in battle. But the more she uses it, the more [[EnemyWithin The Queen's]] attempted [[TheCorruption corruption]] of her body and mind accelerates, being [[HeartIsAnAwesomePower kept in check by only the Tiger Talisman]].
* In Fanfic/TheDearSweetieBelleContinuity, Twilight's research indicates that all alicorns are vulnerable to this if they swing too far to an extreme of [[AnthropomorphicPersonification the ideal or magic they are meant to personify]], explaining Nightmare Moon. It is also implied Celestia went through this during Luna's exile. [[spoiler:Cadance forms one, the Crystal Empress, once she learns of Shining Armor and Luna's affair.]]
* [[spoiler:Count Logan is this for Beast Boy]] in ''FanFic/TheEndOfEnds''.
* ''[[FanFic/Zero2ARevision Zero 2: A Revision]]'' has the Digimon emperor being presented as Ken's dark side whenever he shows up as a result of Demon's Dark Spores. Later, in an attempt to stall the prevent the Digidestined from entering the real world and destroy his entire army [[spoiler: and to keep the Digidestined from evolving their Digimons so that he will remain at full power to combat [[EvilVsEvil Demon]]]], Umbradevimon decides to corrupt Davis, using his own jealousy and hatred for TK against him with the help of the Touch of Evil as well as 15 black gears to create Darkheart, Davis's own evil self. Darkheart at first starts out as an obedient automaton whose only purpose is to keep the Digidestined on their toes under Umbradevimon's instructions. [[FromBadToWorse Unfortunately just as the Digidestined decides to enter the real world and leave some behind to stall him]], Demon inserts a Dark Spore to him which gives him a free will and becomes a sadistic psychopath hellbent on absorbing the Digidestined [[ForTheEvulz just because he can do it]] and [[CardCarryingVillain to become the greatest villain of all time]]. Umbradevimon's plan unintentionally [[GoneHorriblyRight works a bit too well]] as Darkheart [[KnightOfCerebus single-handedly managed to create the]] DarkestHour for the entire Digidestined a long time (13 chapters to be exact) before he finally gets taken down.
* In ''Fanfic/TheBridge'', Monster X's Kaizer Ghidorah transformation serves as this. Monster X is a NobleDemon, while Kaizer Ghidorah is a bundle of hatred and rage. Monster X is roughly equal in strength to other kaiju like Godzilla and Gigan, while Kaizer Ghidorah can curb-stomp them.
* [[Anime/CodeGeass Kallen]] has one in the fanfic ''Fanfic/FairyWithoutWings''. [[spoiler:It's the [[HalfHumanHybrid Etherious side of her soul]]]].
* In ''Fanfic/TheDarkSideOfTheMirrorVerse'', [[spoiler:Mirror Twilight creates the same ManaDrain device as [[WesternAnimation/MyLittlePonyEquestriaGirlsFriendshipGames Human Twilight did]], which ends up draining mana from ponies at the party she's attending, including Mirror Tirek, resulting in it overloading and exploding (as she hadn't absorbed the World Mirror's magic to prevent such a thing from happening). This, combined with her bitterness, hatred, and envy of Princess Trixie, transforms her into Nightmare Spotlight. She promptly rips Canterlot apart to create a floating stage in the sky and [[WhosLaughingNow attempts to kill Trixie to get revenge for the wrongs she thinks Trixie has done to her]], planning to move onto everypony ''else'' she feels did her wrong. All publicly before all of Equestria on a live 'show' to finally get the respect she believes she's been denied all her life.]]
* In the fandom role-play [[https://www.rpnation.com/threads/infamous.69863/#post-2107228 "Infamous: After the Blast"]] and all of its subsequent storylines, the (debatably) main protagonist, Felix Shane, is revealed to have this. Originally thought to be a form of Dissociative Identity Disorder or something similar, it's later revealed that Felix Shane does not, in fact, have any [[SplitPersonality alternate personalities.]] Instead, he actually WANTS to murder all the time, but holds that side of him back whenever possible. However, when he does let it out, he becomes significantly more powerful, as he's no longer holding himself back. This side of him is his Psych/3rd "personality." Contrast with his [[HulkingOut Shadow/2nd personality, who has the same effect but is released through his indomitable rage.]]
* Taiga has a variation in ''[[https://www.fanfiction.net/s/11905736/1/Fate-Gamer-Night-SE Fate Game Night]]'' when she wields her shinnai, which she's stored all her negative emotions in (particularly hatred and anger), turning it into a pseudo cursed sword. Though it's main weakness is that while she does become far stronger, the shinnai contains only a finite amount of power; once her hatred runs out, she turns back.

[[folder:Films -- Animation]]
* ''WesternAnimation/HeavyMetal'' segment "Captain Sternn". While under the influence of the Loc-Nar, Hanover Fiste grows into a mightily muscled hulk and smashes through all opposition in an attempt to murder Sternn. [[spoiler:Once everyone's gone, he turns back. Sternn then thanks him for getting him out of the trial... before shooting him out of an airlock in lieu of payment.]]
* In ''WesternAnimation/TheIronGiant'' the giant is pretty powerful on his own, but friendly. You do ''NOT'' want to push his BerserkButton however.
* Uni-Kitty from ''WesternAnimation/TheLEGOMovie'' is normally a GenkiGirl CloudCuckoolander. However, it's shown she has some pretty bad anger issues, and when sufficiently pushed she transforms into a demonic, red-furred version of herself that can fly and bite [[MechaMooks Micromanagers]] in half.
* The anime movie ''Anime/{{Tekkonkinkreet}}'' has the main character Black get saved [[spoiler:from space aliens by his own Super-Powered Evil Side known as "The Minotaur" which then tries to completely overtake him and show him the true power "The Minotaur" can unleash.]]
* ''WesternAnimation/MyLittlePonyEquestriaGirls2013'': Sunset Shimmer in the first film is a nasty person, but she still has limits; she doesn't kill Twilight when she has the chance, and she lets Spike go rather than trade him for the Element of Magic when she has her chance. When she corrupts herself (with the Element of Magic) into a demon form, she has no such limitations and tries to fry Twilight and her friends without a second thought. She's [[HeelFaceTurn immediately remorseful for what she's done]] after being turned back, and in later movies is able to harness the power of the Elements without becoming corrupted thanks to ThePowerOfFriendship.
* At the climax of ''WesternAnimation/MyLittlePonyEquestriaGirlsFriendshipGames'', [[spoiler: Twilight Sparkle's human counterpart transforms into Midnight Sparkle after being pressured into unleashing the magic inside her magic-absorbing amulet. With this power, she blasts open portals to Equestria all over the place, with little regard for the stability of the non-magical human world. She snaps out of it thanks to Sunset Shimmer.]]

[[folder:Films -- Live-Action]]
* Nathan Wallace in ''Film/RepoTheGeneticOpera'' is a sweet, loving, family man. Until he puts on his helmet, at which point he becomes the merciless Repo Man.
* The version of Venom in ''Film/SpiderMan3'' is Peter's Super-Powered Evil Side, and it begins to affect his personality. The catch is, Venom's just enhancing Peter's latent personality traits, so out-of-costume his evil side comes across as a massive dork, and he is generally an asshole to everyone rather than being a figure of terrible power. Now for Brock, who's already portrayed as an asshole from the beginning, it's a different story.
** It should be noted Evil Pete isn't ''that'' nice. He makes a reasonable effort to kill Sandman and is at least indifferent to whether Harry survives a pumpkin bomb to the face.
* In ''Film/ForbiddenPlanet,'' the ancient alien civilization made a giant machine which is capable of turning thoughts into reality. It turns out that the machine works even better with subconscious thoughts.
* Donning ''Film/TheMask'' unleashes a person's Super-Powered Chaotic Side.
** In the comics, however, it unleashes a more "evil" side to a person, as the eponymous mask takes the driver's seat of their mind.
* In the ''Franchise/StarWars'' franchise, it's possible for a Jedi to temporarily become stronger by tapping into TheDarkSide, but with the [[PowerAtAPrice consequence]] that it can become permanent. It's also not guaranteed to work, since it can backfire and lead to their making stupid mistakes due to being DrunkOnTheDarkSide.
** For example, this is how Luke Skywalker defeats Darth Vader in ''Film/ReturnOfTheJedi'' after being provoked into an UnstoppableRage by Vader's use of the RelativeButton. Palpatine even says it: "Your hate has made you powerful." Luke refuses to kill Vader after defeating him, though he comes very close, and if he had that would have led to [[IfYouKillHimYouWillBeJustLikeHim becoming the new Vader]].
** Per WordOfGod, this is also how his father Anakin defeats MasterSwordsman Count Dooku in ''Film/RevengeOfTheSith'' ... but it has the cost of causing him to edge closer to TheDarkSide. Unlike his son, he gives into his anger and kills Dooku, leading to his fall to the Dark Side later on. And despite believing himself to be more powerful because of this, it leads to him trying a reckless maneuver during his fight with Obi-Wan Kenobi that results in some horrific injuries (which are the reason he needs to wear the black suit in the original trilogy).
%% * Phoenix in ''Film/XMenTheLastStand''.
* Various film adaptations of ''Literature/TheStrangeCaseOfDrJekyllAndMrHyde'', though this is not present in the original book:
** ''Film/VanHelsing'': Hyde is an ape-like man of superhmuman strength.
** ''Film/TheLeagueOfExtraordinaryGentlemen'': Hyde is essentially the Hulk, superpowered brute who is hard to control but ultimately not ''evil''.
* In ''Film/SuicideSquad'', [[TheCutie archaeologist June Moone]] inherits the powerful and evil spirit of [[EvilIsSexy The Enchantress]], and can tap into The Enchantress's evil powers by speaking her name. Amanda Waller attempts to make The Enchantress a member of the Suicide Squad, however The Enchantress gets permanent control of June Moone early on and becomes the main villain instead.
* The premise of the movie ''Film/{{Split}}'' is a man with 23 personalities kidnaps three women to sacrifice them to a Super Powered new personality called The Beast when it emerges. Most of his personalities are decent people, and he is horrified by what he has done when his original personality briefly gets control again. The explanation given for how The Beast has super powers is the idea that a person with Dissociative Identity Disorder can change their bodies based on their beliefs although [[spoiler: the TwistEnding of the movie reveals that it takes place in the same universe as ''Film/{{Unbreakable}}'' where super heroes and villains do exist.]]

* Dialydd Mab is this to Merlin Athrawes, main character of ''Literature/{{Safehold}}'' series. While Merlin is usually calm, composed and tries not to use the entirety of his ImplacableMan skills for fear that it might get him labelled as a demon, Dialydd leaves no survivors, is completely cold and kills without remorse and without any internal limitations. And his name is Welsh for [[NamesToRunAwayFromReallyFast Avenging Son]].
* In ''{{Literature/Redwall}}'', some animals (usually badgers) can go into a [[TheBerserker berserker rage]] called the "Bloodwrath" which makes them ''extremely'' powerful, and able to totally ignore pain... and also no longer able to tell friend from foe, meaning it's dangerous to ''anyone'' who's nearby when they go into this rage.
* In ''Literature/HouseOfLeaves'', Johnny Truant channels his Super-Powered Evil Side against [[EveryoneCallsHimBarkeep Gdansk Man]]. The way in which Truant thrashes him and how the book describes Gdansk Man's wounds afterwards has led to some EpilepticTrees, such as [[spoiler:Johnny Truant '''is'''the Minotaur]].
* Most [[OurWerewolvesAreDifferent werewolves]] that aren't villainous in human form get a lot more powerful and don't mind the taste of blood when transformed. Both the ''Literature/KittyNorville'' and ''Literature/MercyThompson'' series have werewolf choosing their animal form for combat, and the ''Kitty Norville'' series portrays the Wolf as an alternate personality. The Wolf won't go out of its way to KickTheDog, but [[SociopathicHero it won't really care about]] taboos regarding [[ImAHumanitarian cannibalism]] or [[ThouShaltNotKill murder]].
* ''Franchise/{{Star Wars|Expanded Universe}}'': Exar Kun, Darth Vader, Ulic Qel-Droma, Darth Malak... when a [[Franchise/StarWars Jedi]] falls to the Dark Side, it's time to get out of Dodge.
* [[spoiler:Beranabus]], in Darren Shan's [[Literature/TheDemonata demonata]] series. [[spoiler:As a result of being half demon, he was able to turn into one. He does this only once, because he's afraid that this ability is one of these, in order to fight [[CosmicHorror Death]]. He succeeds in his goal of sending it back into the demonata's universe, but dies in the process.]].
* ''Literature/HonorHarrington'': Havenite secret agent Victor Cachat's Evil Side isn't so much superpowered, as it just removes all stops in his ''[[TheUnfettered already]]'' fanatical and [[TheDeterminator determined]] character, turning him into a Death incarnate. Which tends to [[BewareTheNiceOnes scare shitless]] those who know him only as a naive and timid Mister Nice Guy.
* Multiple examples in the ''Literature/SkulduggeryPleasant'' books. [[spoiler: Darquesse, Lord Vile and Shudder's gist come to mind]].
* In ''Literature/TheFirstLaw'' series, Logen Ninefingers is known as a vicious and bloodthirsty berserker called the Bloody-Nine. However, Logen is actually a pretty nice guy who really doesn't like fighting very much. His Bloody-Nine persona is an alternate personality of unstoppable bloodlust. When the Bloody-Nine takes over, Logen becomes superhumanly fast and strong as well as nigh-invulnerable. Logen hates his Bloody-Nine side, however, because he kills everything in sight, friend and foe alike.
* In ''Literature/DeltoraQuest'', when Steven is in danger, he [[spoiler:transforms into/releases [[SdrawkcabName Nevets]], who usually rips apart nearby enemies, along with everyone else stupid enough to get near him]].
* In the ''Literature/MalusDarkblade'' series, the title character can use T'zarkan, the daemon possessing him as this, but with a twist: each time it happens, T'zarkan gains a little more control over him.
* In ''Literature/CountToTheEschaton'', hero Menelaus also has houses the super-powered and amoral Iron Menelaus. Likewise with Del Azarchel/Iron Del Azarchel.
* The ''Literature/DresdenFiles'' have the Denarians, fallen angels sealed in silver coins. So much as touch the coin, and they get a free pass to the back of your mind, to convince you in any way they can to accept their power. Once you do, they go from backseat driver to Super-Powered Evil Side and grant you extreme power, at the low, low cost of [[DealWithTheDevil your immortal soul]]. Over time, the human host starts to become as evil as the Denarian (if they weren't already).
* ''Literature/WildCards'':
** The Radical has the combined powers of all other alter-egos of Captain' Trips, thus making one of the most powerful aces. He's also, depending on where you stand, a WellIntentionedExtremist or a full-blown villain. Obviously he won't let Trips take back the control of his body.
** Greg Hartmann is an amoral, egoistic and hypocritical politician who doesn't care about whom he uses, kills, maims, or hurts in his hunt for power. He is clearly an evil character, but he is absolutely lovely compared to his alter ego Puppetman, a complete sadist and sociopath who uses his potent emotion manipulation power to bring out the worst in everyone and only lives to revel in the violence and horror he creates.
* Literature/TrappedOnDraconica: Halfway transforming into Mordak makes [[spoiler: Kalak]] far more powerful but it also makes him a mindless killing machine.
* Rachel from ''Literature/{{Animorphs}}'' has ''two'' examples: in ''The Separation'' a freak accident with a starfish morph splits her into two Rachels, a 'Nice Rachel' that's timid, ditzy and strategic, and 'Mean Rachel' who gets all of Rachel's BloodKnight instincts but none of her restraint. Later in ''The Return'' Crayak tempts Rachel with godlike power, transforming her into a steel-clawed, indestructible killing machine dubbed 'Super Rachel'.
* Stormform in ''Literature/WordsOfRadiance'' grants the Parshendi the power to call lightning and [[spoiler: invoke an Everstorm]], but in order to enter it you have to bond with a spirit of pure hatred.
* In ''Literature/TheZombieKnight'', hyper states count as this when the [[BondCreatures reaper-servant pair]] isn't old enough and well enough synchronized to control them. For years after they first unlock the state, using it puts them in a state of self-hypnosis where they're [[TheBerserker driven solely by the desire to attack]]. When [[spoiler:Harper and Darsihm]] (bonded for ~30 years) use ''pan-rozum'', the fact that they were able to maintain a small "whitelist" of souls they shouldn't target was an amazing feat of control, and even that was nearly a disaster since there were hostages around whose souls they hadn't memorized.
* In the ''Literature/ParadoxTrilogy'', this afflicts symbionts. The alien implant which grants a symbiont its powers can take control of the host's body in his sleep; while it isn't exactly sentient, it is full of bloodlust and hatred and will hurt anyone the host cares about if it can.
* Myrren Kahliana in ''Literature/DarkHeart'' discovers she has one as she learns to use her magical powers. It saves her life more than once, but [[JekyllAndHyde when it comes out, it doesn't want to go back in]].
* In ''Literature/TheLordOfTheRings'', the bearers of the Elven Rings are terrified of acquiring a Super-Powered Evil Side should they ever come into possession of the One Ring. The One Ring would give them far greater powers than the ones they already have, but would simultaneously also corrupt any achievements that the Ring had made possible, no matter how benign their original intentions were.
* ''Literature/EgilsSaga'': When Egil's father Skallagrim is in a fit of 'shape-strength', he is even stronger than usual but also an incontrollable madman who kills indiscriminately. When Egil is twelve and playing at a ball-game against his father and it looks like Skallagrim is going to lose, he suddenly becomes 'shape-strong' and kills Egil's best friend Thord, his nanny Thorgerd, and very nearly Egil himself.
* In ''Literature/TheOtherKindOfRoommate'', Xander is very rightly this to Alex. On top of being ten times more of an aggressive and amoral personality, complete with every [[SirSwearsALot profanity known to man]], plus a few he strings together, he's the half with chock full of the enthusiasm needed to use their powers' [[KillEmAll final setting]].
* In ''Literature/WingsOfFire'', [[TheBigGuy Clay]] thinks he has a suppressed bloodlust in him due to having attacked the other dragonets at their hatching, causing the dragons raising them to think he's a monster. [[spoiler:It turns out to be subverted, when it's revealed that Clay's "attack" was BigBrotherInstinct, helping the others hatch.]]
* In the ''Literature/DreambloodDuology'', Gatherers are well trained and educated priest capable of killing people in their dreams and making them enjoy it. [[OurVampiresAreDifferent Reapers]] are Gatherers who have lost control and become addicted to the [[FantasticDrug dreamblood]] they collect as their job. Those are capable of killing hundreds or thousands of people at the same time just to get their desired dreamblood.
* ''LightNovel/DateALive'' has Inverse Form, a state which Spirits enter if they pass the DespairEventHorizon. In Inverse Form, a Spirit is far more powerful and also lacks any sense of restraint. Their weapon, previously referred to as an "Angel", is replaced by a darker counterpart called a "Demon King".
* ''Literature/VillainsByNecessity'': [[spoiler:Sam]], courtesy of Valeriana's medallion.

[[folder:Live-Action TV]]
* Niki in ''Series/{{Heroes}}'' has her amoral alter ego Jessica ("[[FanNickname ikiN]]"), who has sole control of her super strength [[spoiler:until the finale, when Niki finally gets to use it for herself. She might have used it once on impulse a few episodes prior to stop an attacking policeman--this is debatable.]]
** In the second season, it was explained that [[spoiler: some people suffer a dissociative break to cope with the new reality of being a metahuman. When Niki conquered the Jessica persona at the conclusion of the first season finale, she manifested a third personality named Gina several weeks later.]]
* A really beautiful [[DeconstructedTrope Deconstruction]] is the British TV series ''{{Series/Jekyll}}''.
* Lori developed one in the ''Series/BigWolfOnCampus'' episode "Manchurian Werewolf" after being bit by a brainwashed Tommy. She became a member of the werewolf syndicate. Merton also got a dose of the evil life in "Everybody fang chung tonight" and "Boy who tried wolf" where he become a vampire and a werewolf.
* Every HeroicVampire protagonist or Supporting Character: see ''Series/ForeverKnight'', ''Series/{{Angel}}'', and ''Series/{{Moonlight}}''.
* ''Series/KamenRiderKabuto'''s Tsurugi Kamishiro is actually [[spoiler:the Scorpioworm]], who actually manages to [[spoiler:overpower both Cassisworm Clipeuses when he was unable to defeat even one as Kamen Rider Sasword]].
* In ''Series/KamenRiderKuuga'', Kuga's Ultimate Form [[spoiler: could possibly make its user become the ultimate evil and destroy the world and has a kick capable of doing said act]].
** The ''Series/KamenRiderDecade'' version of Kuuga also possesses this form but [[spoiler: unlike the original, he remains the evil 'Black Eyed' version his entire run in this form]]. Taken further when he gains Rising Ultimate form which [[spoiler: first used as a mindcontrolled [[TheDragon Dragon]] by the BigBad]].
*** Decade gains an evil alternate form in his Violent Emotion form, which [[spoiler: turns him into a destroyer of realities]].
* In the live-action ''Series/PrettyGuardianSailorMoon'', [[spoiler:Sailor Moon's alternate persona Princess Serenity is a Super-Powered LoveMakesYouEvil Side]]. The second half of the series is spent just trying to contain her, and upon the realization she can't be contained, at least minimize the damage she causes.
* In the ''Series/{{Farscape}}'' universe, starving [[PlantAliens Delvians]] start sprouting growths that paralyze any predators that touch them, turning would-be predators into prey. If that doesn't help, they'll start emitting spores, gradually paralyzing any and all lifeforms in the vicinity. In this state, higher cognitive functions are compromised, gradually turning them more and more feral. And if the said Delvian is [[TheAtoner Zhaan]] who was nice only due to her HeroicWillpower in the first place...
* ''Series/BuffyTheVampireSlayer'' has two of these:
** If Series/{{Angel}} loses his soul (due to the lingering effects of a GypsyCurse), he becomes the [[ChessMaster brilliant]] and formidable Angelus, widely reputed to be the most vicious vampire in history. As Cordelia Chase once [[LampshadeHanging queried]] about Angelus's evident [[EvilGenius genius]] compared to his heroic alter ego's, "...what is it about [[EvilIsCool evil]] that jacks up the I.Q. points?" More emphasis on the evil, though.
** Played with for a bit in his own series where he becomes a SED KnightTemplar version of himself: as Angelus he'll gloat and joke and dream up sadism. As a frightening mix of the two Angel is basically the most vicious vampire in history, on our side.
-->Let them fight the good fight. Someone has to fight the war.
** When Willow [[BreakTheCutie is pushed to the snapping point]], she unleashes a Super-Powered Evil Side [[WoobieDestroyerOfWorlds in a ''bad'' way]], replete with utterly delightful badass one-liners. [[PunctuatedForEmphasis I. OWE. YOU. PAIN.]]
** The depth of this is such that Willow, the cutest, sweetest, and most innocent of the Scoobies at series start, becomes the only non-Giles member of the Scoobies to have directly murdered an innocent person. (Glory wasn't innocent, but the human Ben was)
** The emphasis here is on the superpowered - Dark Willow is arguably the most powerful known being in the Buffyverse.
** As time goes on, Willow seems to have her Super-Powered Evil Side under control. It's more that she turns evil when she uses powerful magic, but then she turns back good when she stops. A scene in Season Seven demonstrates this effectively: while using a powerful barrier spell to protect an innocent girl from a spider demon, Willow gets the black eyes and black hair, and also calls the girl a bitch. After the demon leaves, she goes back to normal, and apologizes to the girl.
* ''Series/{{Smallville}}'':
** Clark's "Kal" persona [[spoiler:when he is affected by red kryptonite]].
*** The episode ''Exile'' deserves a special mention. It is a full episode of Clark doing everything ever linked to the word {{Superdickery}}, including but not limited to [[BankRobbery robbing banks]] ([[KickTheSonOfABitch beating up the would-be robbers on the way]]), [[KickTheMoralityPet roughing up Chloe]] after [[IKnowYoureInThereSomewhereFight she spent two months trying to convince him to go home]], making a [[DealWithTheDevil deal with a crime boss to break into a high-security vault]] and [[CallingTheOldManOut coming to actual blows with Jonathan]]. Oh, he [[ArsonMurderAndJaywalking stole and destroyed Chloe's class ring too]]. [[spoiler:He is actually affected by the red kryptonite in Chloe's ring, and breaking it finally frees him from his Super-Powered Evil Side.]]
** There's also Kal-El, Clark's EnemyWithin who uses his powers a lot more efficiently and can even fly.
** [[spoiler:Isobel the witch]] becomes this for Lana in season four.
** [[spoiler:Davis Bloome in Season 8 has perhaps the ulitmate Super-Powered Evil Side in Doomsday, an alien SerialKiller and PersonOfMassDestruction that is trapped inside of him. The good news: it's possible to repress Doomsday. The bad news: the only way to do it is for Davis to commit murders as himself, a fact that slowly drives him insane, even as it lets him access Doomsday's power while he's in his own body.]]
** Gordon Godfrey has [[spoiler:{{ComicBook/Darkseid}}]] in season 10.
* ''Series/TheIncredibleHulk'': In "Dark Side", David suppresses one side of his brain and succeeds only in letting his, well, dark side take over. He still doesn't kill anyone, but the usual halfway-point-Hulk-out-that-doesn't-affect-the-plot is much more interesting than usual.
** This was played with in another episode, wherein David discovered that a small-town scientist had succeeded in creating a hulk-like creature decades ago. Reading through the scientists' notes in hope of getting insight into a cure for his own condition (while being assisted by the now-elderly lab assistant who had originally transformed many years ago), David reads a observation by the scientist that the creature is murderous and cruel, and notes that he believes it is due to the inherent personality of the human subject. Cue an OhCrap by David as he realizes there's a secret reason why the lab assistance is being so helpful in trying to recreate the process that made him into a Hulk. The early Hulk wasn't an evil side, it was just the ''already'' evil personality of the lab assistant with the strength to do as it pleased.
* Sam Winchester, ''Series/{{Supernatural}}''. When he taps into the demonic "special child" aspect, he is extremely powerful (telekinesis, exorcism, torturing/killing of demons, immunity to attacks by demons) but loses all his humanity and morality and becomes arrogant, violent and cold. His eyes turn yellow or black on a couple of occasions.
** And Dean Winchester, in a way. In season 10, [[spoiler:The Mark Of Cain turns its bearer into a heartless evil murderer who loves brutally killing everyone, and has the potential to turn them into a demon]], and demons tend to have super-strength. In the past, Dean would punch an angel and doing it is like punching an iron wall; Painful. In Season 10, [[spoiler:the Mark turned Dean into a demon, he was cured and turned back into his human-self, but the Mark still affected him and slowly turned him into this cold-blooded killer. I'd say it also enhanced his raw physical strength because he managed to beat the crap out Castiel; an angel he already punched before, but it didn't even left a mark and he nearly broke his hand hitting him. Yet Dean was able to beat the same angel into a bloody mess and leave him laying on the floor with probably a broken nose. Now, granted Castiel wasn't at full strength at the time, but Dean also punched Cupid once and almost broke his fist, and surely Castiel would still remain stronger than a low-ranking Cupid, even when he's half-de-powered... right?]]
* The 'good' vampires on ''Series/TheVampireDiaries'' are [[TheSoulless this]] when their [[GoodIsNotNice humanity]] is [[TinMan turned off]]:
** Subverted. Stefan Salvatore is a great example of this when he becomes the Jekyll&Hyde Ripper.
** Elena Gilbert's non-humanity side is also subverted. Not necessarily different in physical strength, but also much more cold, arrogant, ruthless, and even calculating that the Salvatore brothers have to keep a sharp eye one her. They did their best trying to bring her back to her old self again. She also happens to be extremely fearless when she's in this phase.
** Even Caroline Forbes's is a pretty straight example. She was even more capable of putting her brute strength and compelling abilities in use without hesitation, especially when she forced Stefan to turn his humanity off to save his niece.
* In ''Series/LostGirl'', Bo has a major Super-Powered Evil Side, draining a whole room of people of their life force when someone is about to kill her lover.
* The Doctor from ''Series/DoctorWho'' is seen as this by John Smith, his temporary human self in "Human Nature[=/=]The Family of Blood".
** The Time Lord Victorious and the Valeyard both qualify as this to the Doctor.
* ''Series/StarTrekDeepSpaceNine'': In "The Alternate" episode, Odo temporarily gets a Super-Powered Evil Side after being exposed to a psychotropic gas on L-S VI. Its effects cause him to [[InvoluntaryShapeshifting involuntarily transform]] into a monstrous form, driven by rage and self-preservation.
* ''Series/TheCrowStairwayToHeaven'': In lieu of 22 non-stop episodes of a demented supernatural killer running about creating mayhem, the TV series of the film of the comic book created a personality split for Eric, where the Crow persona takes over when he becomes enraged or is under particular stress, or someone uses magic to make it happen.
* In ''Series/PowerRangersInSpace'' [[spoiler:this was one of the biggest parts of the entire plot. [[BigBad Astronema]] was actually the Super-Powered Evil Side of Karone, who was Andros' sister, kidnapped and brainwashed as a child. When [[TheReveal she found out]] she made an honest attempt at a HeelFaceTurn, but [[BiggerBad the Dark Specter]] had other ideas, and she became even worse than before. Eventually, her evil side was banished forever by Zordon's HeroicSacrifice, and she became a hero in her own right.]]
* In the third season of ''Series/TheFlash2014'', Caitlin starts manifesting her Earth-2 counterpart's superpowers. Eventually, this starts to result in the Killer Frost persona taking over, complete with white hair, icy blue eyes, and a reverbing voice, not to mention the cold powers. It's made clear that Caitlin and Frost are constantly struggling for control. This is foreshadowed by Frankie Kane, whose body is occasionally taken over by her Flashpoint counterpart Magenta, with glowing magenta eyes, an evil smile, and metal control powers. Barry is able to talk Frankie into reining Magenta in, though. (As for Caitlin, after a several-episode run in full Killer Frost mode, when Savitar is on the verge of finishing Cisco off, she finds she can't bring herself to allow it, and returns to Team Flash for the final battle - but ''not'' to her original pre-powers personality. Even she isn't sure who she is anymore, and pulls a TenMinuteRetirement while she rediscovers herself between seasons.)
* In ''Series/{{Supergirl 2015}}'', Samantha Arias is an average single mother who eventually discovers she has Kryptonian powers, but can't activate them at will, only during stressful situations. Her cold and ruthless "Reign, the Worldkiller" persona has full control over her powers, and is even more powerful than Supergirl. [[spoiler:In their first fight, she beats up Supergirl so badly she is broken and bleeding and needs to be hospitalized, while Reign doesn't have a scratch on her despite taking several hits.]]

* [[http://www.youtube.com/watch?v=_wA5NmQESx8 "Down With The Sickness"]] by {{Music/Disturbed}}. Also [[http://www.youtube.com/watch?v=VyctTU_0FiM "The Night"]].
* "[[http://www.youtube.com/watch?v=cG5LNNUGs40 The Art Of Subconscious Illusion]]" by Music/AvengedSevenfold
* [[http://www.youtube.com/watch?v=z9_QQIWNovc Revenge Syndrome]] by [=MafuMafu=] is about a girl whose evil side emerges to [[BullyHunter slaughter her tormentors]].

[[folder:Myths & Religion]]
* OlderThanPrint: Cuchulainn in Myth/IrishMythology has a prime example of this kind of UnstoppableRage. In the epic, ''[[Literature/TainBoCuailnge Táin Bó Cúailnge]]'', he enters a "Ríastrad" or "Warp Spasm." In this state he [[PainfulTransformation transforms]] into [[OneWingedAngel a horribly mutilated monster]] whose very appearance is enough to scare enemies away. The catch is that, while in this form, Cuchulainn may not know friend from foe. (See ''ComicBook/{{Slaine}}'' from ''ComicBook/TwoThousandAD'' to see just ''how'' mutilated he looks.) In some stories, Cuchulainn must wear a [[PowerLimiter special girdle or harness]] to keep his body from tearing itself apart when the warp spasm takes him.
* Kali is this to Durga/Parvati in Myth/HinduMythology.

[[folder:Pro Wrestling]]
* This trope is a tradition in Japanese pro wrestling, where many wrestlers unveil an evil persona to face a special threat or to play mindgames with a rival, and sometimes get in storyline overcome by these personas and turn fully heel, because EvilIsNotAToy. Among them there are Keiji Muto's "Great Muta" and his many emulators, The Great Sasuke's "SASUKE", HardGay's "Super HG", [=BxB=] Hulk's "Killer Hulk", Gamma's "Gamma Daio", Kikutaro's red mask, and many others.
** In 1996, Japanese wrestler Wrestling/JushinThunderLiger, who traditionally played the role of a face, unveiled his "Kishin Liger" heel persona, when he wrestled heel wrestler the Great Muta, who mid-match ripped Liger's mask off, revealing his "oni face". Liger's wrestling style would become notably more aggressive and heel-like in this persona.
* This was Wrestling/MickFoley's schtick for a while in the WWE: when he needed a "boost" for a match, he'd come out as either his [[WithGreatPowerComesGreatInsanity Mankind]] or [[AxCrazy Cactus Jack]] persona.
* [[Wrestling/HunterJohnston Delirious]] will swap out his green attire for red attire when one of his enemies has made the mistake of making him ''really'' angry, using more heelish tactics and weaponry, and even spitting poison mist in people's faces.
* There are hints that this is what is happening when Wrestling/FinnBalor puts on the Demon war paint for big matches.

[[folder:Tabletop Games]]
* This crops up in the various ''TabletopGame/OldWorldOfDarkness'' RolePlayingGames, especially those featuring Vampires and Werewolves.
** One TagLine for the original ''TabletopGame/VampireTheMasquerade'' was "A Beast I Am, Lest A Beast I Become" -- leeches had to allow themselves little atrocities like controlled blood-drinking to avoid being consumed entirely by the madness of their inner blood-hunger. However, while in the thrall of such a state, vampires can ignore wound penalties, which is a significant combat asset.
** ''TabletopGame/WerewolfTheApocalypse'': Werewolves, on the other hand, don't tend to view their own [[UnstoppableRage berserk frenzies]] as "evil" (after all, Rage is a gift from Luna... and they have plenty of reason to be really, really pissed off). However, if they give in to their Rage ''too'' fully, they can enter a state called "Thrall of the Wyrm," just like a normal frenzy, except that it's inescapable, and tends to provoke rather horrific behavior (typically either cannibalism, rabid dismemberment, or... erm... defilement).
** In ''TabletopGame/ChangelingTheDreaming'', changelings can get magic ("Glamour") from normal humans two ways -- the first is by inspiring them to do something incredible. The second is to "ravish" them -- make them feel despair. One example of this involved convincing a small child that the Fae in question had just ''murdered the Tooth Fairy''.
** ''TabletopGame/WraithTheOblivion'': Wraiths have got their Shadow, a second personality usually existing within the wraith trying to make them them give up their struggles and descend into nonexistence or permanently hand over control of their body. Depending on the Shadow, this might take many forms, some direct and some seemingly helping the wraith. The latter type often has ways to enhance the wraith's body when temporarily in control - better attributes, more magic powers or even items appearing only during the Shadow's catharsis. Such wraiths then always have the ability to let their Shadows handle combats too tough for them, but are generally loathe to do so because there's no telling what else the Shadow might do while in control.
** ''TabletopGame/KindredOfTheEast'': Being a kind of vampire, Kuei-jin must keep their amoral lower soul (P'o) under control, lest it takes over them in a frenzy of carnage. It's not an easy thing to do since each Kuei-jin's P'o is out of balance, compared to the living. Some Kuei-jin Dharma try to make good use of this evil side, though.
* The ''TabletopGame/NewWorldOfDarkness'' keeps much of this:
** In ''TabletopGame/VampireTheRequiem'', vampires have the Beast within, which compels them to feed.
** In ''TabletopGame/WerewolfTheForsaken'', werewolves have two degrees of rage: one where they have to kill ''something'', and another where they have to kill ''everything''.
* ''TabletopGame/{{Exalted}}'' has a couple instances where the characters go temporarily insane on some level:
** The Solar Exalted might have this particular category nailed; one of their abilities -- Ascendant Battle Visage -- places them into a battle-trance that physically changes them to reflect their BattleAura, and grants them intense and brutal combative skill. Remaining in this state too long, however, sends them into an UnstoppableRage, at which point they become even deadlier, and fight until either they're dead or everything else that might be considered an enemy is dead.
** The Ghost-Blooded (in the 1st edition at least) could learn a certain Arcanos called Lower Soul Ascendant, which fits this trope to a T -- increased physical power at the cost of embracing sociopathic behavior.
* And to round out Creator/WhiteWolf's systems: In ''TabletopGame/{{Scion}}'', the Scion Companion supplement adds the Tuatha Dé Danann to the playable pantheons. One of their pantheon specific abilities? The "Rí­astrad" mentioned in the above mythology entry.
* In ''TabletopGame/DungeonsAndDragons 3.5'', there is a prestige class called Frenzied Berserker. Once they've Frenzied, which is like a Barbarian's Rage but moreso, they attack until either the frenzy runs out, they are incapacitated/dead, they pass a will save, or there's nobody nearby.
* Highly common in ''TabletopGame/Warhammer40000'', and one of the reasons Space Marines (Grey Knights in particular) are required to pass such rigorous and often deadly mental trials as a method of prevention. The most obvious are the Blood Angels Chapter and its successor chapters, whose members are known to succumb to a condition called the Black Rage which increases their already SuperSoldier levels of strength and vitality and turns them into frothing berserkers who seek only death, often organised into aptly-named Death Companies led by skull-helmeted {{Badass Preacher}}s. [[OurElvesAreBetter The Eldar]] however create one of these ''intentionally'', inducing a form of split personality disorder so that in battle they can fight with unhindered skill and brutality while retaining absolute control over themselves the rest of the time. Then there's Chaos, which, being TheCorruption and AlwaysChaoticEvil personified, fully embraces the added power this trope provides with no concern for the consequences, because "sanity is for the ''weak''".
** And then there's the Possessed Marines, who have a Super-Powered ''Super Evil'' side.

* Takanuva gets one of these in ''Toys/{{Bionicle}}'', after having some of his Light drained by a Shadow Leech.

[[folder:Video Games]]
* For some reason, having an "evil/dark side" was a really popular game mechanic in the early 2000s.
* Ryu, from the ''Franchise/StreetFighter'' series, has a power inside of him known as the Satsui no Hadou, or Surge of Murderous Intention, which he works to suppress and was retconned as the reason that Sagat received the scar he bears on his chest. Akuma (Gouki in the Japanese version) represents someone who has fully given in to the Satsui no Hadou, and when he's not holding back, he is truly fearsome. In ''Street Fighter Alpha 2'' and ''3'', Evil Ryu is actually a secret, playable character (a dark-skinned, red-eyed version of Ryu with some additional attacks that were borrowed from Akuma).
** Ryu's Super-Powered Evil Side is a result of his being unable to control the power. However, since the power still involves a willingness to kill and a more brutal mindset even when in control, he makes no effort to even try to learn how.
** Evil Ryu returns to the ''SF'' storyline through ''Super Street Fighter IV'', where he's a playable character. This time he has gone from merely a dark-skinned, red-eyed Ryu to a borderline PersonOfMassDestruction with a kanji carved on his flesh and a glowing orb where his heart should be. [[spoiler: Making Evil Ryu return to the surface was a plot point in the ''Ties that Bind'' tie-in anime. It almost works.]]
** Oni represents this to Akuma. Whereas Akuma does have some degree of control over the Satsui no Hado, Oni is Akuma when the Killing Intent finally consumes him. Oni drops the moral code of only fighting worthy opponents that Akuma held to, and will fight, and even kill, anybody and everybody he comes across. Oni is the one thing Akuma ''doesn't'' want to become. And the most terrifying thing is that Oni is miles above most other fighters, with only a handful including ''Cody and Gouken'' able to challenge him.
* In ''VideoGame/PrinceOfPersiaTheTwoThrones'', the Prince occasionally transforms into an alter ego with a bladed [[ChainPain chain]]-[[WhipItGood whip]] (and [[PossessionImpliesMastery the skills to wield it gruesomely, out of nowhere]]) and who can completely regenerate whenever exposed to the Sands of Time, but at the expense of constantly deteriorating health otherwise. The Dark Prince is also a sociopath with a massive entitlement complex. Even when in the Dark Prince body, the Prince remains in control, but the Dark Prince hints that the health draining out of you is actually going into it, and that dying of this will give the Dark Prince control of the body (and, incidentally, Babylon).
* Soma Cruz in ''VideoGame/CastlevaniaChroniclesOfSorrow'' is the reincarnation of Dracula, while Alucard is Dracula's son. The emergence of their Super-Powered Evil Sides are Alucard's greatest fear and Soma's bad ending.
* The Slayer from ''VideoGame/BaldursGate II'', a ten-foot tall spiky mass of pure murder that the protagonist can use and [[spoiler:results from channeling the power of Bhaal, the murder god who fathered the PC]]. An interesting example in that the Slayer seems to have [[spoiler:been part of the PC all along, and only surfaces when the PC loses their soul.]] Using it results in a reputation loss, except for scripted events that force you into it. Plus there's the whole thing about it [[HeroicRROD killing you]] ([[WeCannotGoOnWithoutYou and thus ending the game]]) if you stay in that form for too long.
* Then there's the Slayer's {{Expy}}, the Ravenous Incarnation from ''VideoGame/NeverwinterNights2: Mask of the Betrayer''. The Spirit-Eater curse can grant some pretty incredible powers if you feed enough...problem being that the curse is, you know, a ''curse'' - an utterly empty blight upon the spirit backed by divine malice - and will overcome you, drive you insane, push you to devour the spirits of all you see in an animal frenzy, and finally obliterate you so entirely that even your soul is destroyed forever. Giving in to your hunger for spirits to get more power speeds up that process a ''lot''.
* Dizzy from ''VideoGame/GuiltyGear'' has a similar problem with one of her sentient wings. She's VERY powerful and unleashing her true powers causes her to lose control to her evil wing, Necro, whose motto is "Destroy everything!". With Dizzy being a FriendToAllLivingThings this really troubles her.
** Not that the other wing, Undine, is much better. Unlike Necro, she won't attack anyone who comes within reach randomly, but she ''will'' annihilate anyone she perceives as even the slightest threat to Dizzy without even a second thought... and her definition of "threat" is just a little bit too broad for Dizzy's tastes. Undine is the wing that unleashes Dizzy's version of Gamma Ray... that says it all. Oh, and her tail has a will of its own too and often eats anything within biting reach.
* Rozalin from ''VideoGame/Disgaea2CursedMemories'' manifests a Super-Powered Evil Side during the storyline when her seal is broken, which turns to be [[spoiler:her former life as Overlord Zenon, complete with both memories and power, back from the dead]].
** Mao from ''VideoGame/Disgaea3AbsenceOfJustice'' has a similar Super-Powered Evil Side that can [[spoiler:go on a complete rampage in one of the endings]].
** While not "evil" so much as mindless, Usalia from ''VideoGame/{{Disgaea 5}}'' transforms into a berserk beast when she goes without curry for too long, as a result of Majorita's curse. [[spoiler:The love of her parents plus the release of her own mental and emotional burdens causes the curse to devolve into her SuperMode when they take an attack from Majorita meant to kill her.]]
** Also from ''Disgaea 5'', [[spoiler:Killia has an alternate form where he reverts to his past identity as the ruthless, destructive Tyrant Overlord Killidia, which he can temporarily postpone by consuming a whole meal... though by the end it stops being adequate, and he needs to eat increasingly larger portions to keep Killidia at bay. Coming to accept his past identity without giving in to his urges is what causes Killidia to ''become'' his SuperMode.]]
* From ''VideoGame/LaPucelleTactics'', [[spoiler:Croix has his Super-Powered Evil Side as the Dark Prince serving the fallen angel Calamity.]]
* Iori Yagami in ''VideoGame/TheKingOfFighters'' is normally amoral, and (judging from his winposes) has quite a few screws loose. Riot of the Blood Iori, however, has absolutely no sense of self-restraint and will attack anything on sight.
** Leona also fits this trope, sometimes even more perfectly than Iori, because she is in the "good side" while Iori can't decide himself; with some EmotionlessGirl spices added, though that said, she has smiled [[http://img694.imageshack.us/img694/7456/kof96ika35.gif once]].
* Jaster Rogue in ''VideoGame/RogueGalaxy'' does this, although his "evil" side isn't so much evil as so far above everyone else that he [[AGodAmI barely notices they exist]]. Hard to tell the difference from the "normals" point of view, though.
* Johnny Garland gains this far into the third ''VideoGame/ShadowHearts'' game. [[spoiler:Johnny actually died at a very young age along with his sister, Grace. Their father managed to get his hands on the series' {{Tome of Eldritch Lore}}, in hopes of resurrecting them. He only succeeds in reviving Johnny, as his sister gives up her humanity in order to save him, leaving her an empty shell, "Lady". Because Johnny's body is composed of both "Malice" (negative energy) and "Will" (the human soul/spirit), after being fatally wounded by Killer, his "true" Malice form, the Awaker, emerges.]]
* In ''VideoGame/{{Xenogears}}'', one of the primary villains for the first half of the game, Id, [[spoiler:turns out to be an alternate personality of the primary hero, Fei. Id was completely different from Fei in appearance (except for the face itself) and had several magnitudes more power than him. Shown in a flashback to defeat a half dozen [[HumongousMecha Gears]], unarmed, with a single hit each.]]
** When Id manifests, [[spoiler:even ''[[HumongousMecha Weltall]]'' gets a Super-Powered Evil Side, transforming into Weltall-Id.]]
** This is subject to the variation mentioned at the top of the page. Even though Id doesn't get as much screen time as his alter-ego, [[spoiler:Fei is a personality built on top of Id and the Coward (the original personality). Id is able to access the memories of the Contact, which Fei is only able to do near the end of the game.]]
** Grahf plays this role in two ways. [[spoiler: He is the metaphysical alter-ego of Lacan, a previous incarnation of Fei, and the (current) physical alter-ego of Khan Wong, Fei's father.]]
* Zero of the ''VideoGame/MegaManX'' series gains several powerful new abilities when he is exposed to large quantities of TheVirus. When he is fully awakened by the Sigma or Zero Virus, he loses all of his emotions and his personality shifts to the that of a cold-blooded killer.
* In ''VideoGame/MegaManStarforce'' Pat has a personality disorder. He'll randomly go into an evil state named "Rey" and punch someone. This foreshadows him fusing with Gemini and becoming Gemini Sparks W and B.
* Elena's alternate personality Millenia from ''VideoGame/GrandiaII''.
* ''Franchise/KingdomHearts'':
** Anti-Sora from ''VideoGame/KingdomHeartsII''. Ironically, while Anti-Sora looks ''damn cool'', he's not actually much more powerful than Sora in terms of offense, and can do nothing other than attack solo in a frenzy of clawing and kicking. The inability to heal, gain experience, or really do ''anything'' else makes this form a liability, and it can't be entered deliberately.
** Riku, on the other hand, plays this trope straight in four of the games[[note]](in chronological order: [=KH1=], Chain of Memories, [=358/2 Days=], and [=KH2=])[[/note]], but primarily in ''VideoGame/KingdomHeartsChainOfMemories'' when you can play as him and "Dark Mode" is one of his key abilities. Interestingly, he no longer has one as of ''[[VideoGame/KingdomHeartsDreamDropDistance Dream Drop Distance]]'', but only because his control over his dark powers has improved to the point where he can use them freely without transforming.
* In ''VideoGame/MetroidPrime3Corruption'', Samus gets the ability to enter Hypermode, fuelled by the evil substance known as Phazon. Staying in this mode for too long corrupts her, leading to a NonStandardGameOver, specifically turning into another Dark Samus.
* Dark Jak from ''VideoGame/JakAndDaxter'', after being exposed to [[{{Phlebotinum}} Dark Eco]].
** And then they added a Super Powered ''Light'' Side along with Dark Jak in ''VideoGame/Jak3Wastelander''. You use both to solve puzzles.
** ''VideoGame/JakAndDaxterTheLostFrontier'' gave one to Daxter as well, although the bunny-ears are not good for its badass credentials.
* Franchise/SonicTheHedgehog has one in ''VideoGame/SonicUnleashed''. At night, he'll turn into Sonic the Werehog, a bulky werewolf-esque form of himself with super strength and stretchy arms. Though his personality remains more or less the same except for the obligatory howling.
** This exception is {{lampshaded}} after it is revealed that [[spoiler:Chip is actually Light Gaia, a benevolent spirit, who is guarding the earth.]] Sonic then asks, if it could be Chip who keeps him from succumbing to Dark Gaia and becoming evil when in Werehog form, to which Chip replies that he has nothing to do with him, it's Sonic's kind heart alone which lets him keep his sanity.
** ''VideoGame/SonicAndTheSecretRings'' introduced the Darkspine form, which Sonic transforms into by using the World Rings of [[UnstoppableRage rage]], [[ThePowerOfHate hatred]] and [[AngstNuke sadness]].
* In ''[[VideoGame/SuperSmashBros Super Smash Bros. Brawl]]'', some of the Final Smashes have this effect.
** Bowser's Final Smash transforms him into the ''even more'' monstrous Giga Bowser. Whether or not Bowser was evil to begin with [[DependingOnTheWriter depends on the game you reference]]...
** Luigi's Final Smash, according to its trophies, is "a reflection of the DarkSide he embraced in his brother's shadow."
* Almost every member of the Mishima family in the ''VideoGame/{{Tekken}}'' series is affected by the Devil's Blood, a curse that while it makes them stronger and grants them demonic powers, at cost of their humanity. Also Ogre/True Ogre.The Devil's blood affects the personality of those inflicted, and it's virulent where the host struggles to keep control.
** Devil Jin is esentially Jin Kazama overcome by the Devil Gene, unlike his human form, he's ruthless,cruel and sadistic, enjoying seeing his foes suffer, his alter ego, Jin Kazama tries at all costs to prevent the Devil's blood to take control.
** Kazuya Mishima was originally stricken when he thrown off the cliff by his father in order to survive, originally Kazuya was a good man with a kind heart, but the Devil's blood slowly consumed him, until Jun Kazama awakened in Kazuya his good side that fought off his demonic side. After Tekken 2, though, Kazuya's good side is suppressed by the Devil's blood and Kazuya made an agreement with it and he's able to control the form as he pleases. A shred of his humanity can be seen in his T5 ending where he defeats his grandfather and holds him in his arms, smiling at him and remembering his few happy childhood moments, before the Devil's blood takes control and kills him.

** Heihachi Mishima is just that evil, [[BadassNormal he doesn't need an evil side to get more evil, super powered or kick ass]].
** Jinpachi, who is affected by the Devil's blood, turned into a demon after he died underground under Hon-maru, imprisoned by his son Heihachi, after the events of Tekken 4 Jinpachi is released, and he holds the King of Iron Fist Tournament 5 to find somebody to stop him, as he could feel the Devil taking over. He also sends a letter to Wang, his old friend, to have a go as well.
** [[TheHero Jun Kazama]] counts as well. Turns out she's Unknown, a superpowered... well, where she sits on good and evil hadn't been established, but she basically turns into ComicBook/{{Venom}} and becomes a little more dangerous.
* ''VideoGame/SoulSeries'':
** In the early ''Soul Calibur'' games, Nightmare was supposedly a Demonic-Sword-induced version of this for Sigfried. The latter freed himself in [=SCIII=], but his armor and residual evil power was [[EnemyWithout too attached to Soul Edge to die]].
** Two far more definitive examples show up in ''[=SCIII=]'' as the boss [[NightmareFuel Abyss]] (spawned from Zasalamel's quest for the power to die), and bonus boss [[SNKBoss Night Terror]] (Nightmare on 'roids).
* ''VideoGame/FightersDestiny'' has a clown character, and there's a cheat you can use which turns him into a werewolf.
* ''VideoGame/{{Primal}}'' has its main character who personifies this when in any of her monster forms.
%%* Subverted in ''VideoGame/MuppetMonsterAdventure''.
* It is revealed in ''VideoGame/DotHackGU'' that Natsume has a split personality: Her normal self is her cheery, slightly ditzy self while her other self is crazed, rampaging Pker known as The Edgemaniac. This is played for laughs.
** In the movie adaptation, Haseo's B-St Form. [[TheWorfEffect Even if all it did was make him look pathetic against the final boss...]]
** Haseo's Avatar, Skeith, is also portrayed as this, although Haseo usually does a better job of controlling him than normal for the trope. Skeith is ''seriously'' scary when out of control, his actions being the only thing in the games that actually seem to frighten Haseo.
* ''Franchise/FinalFantasy'':
** Vincent Valentine from ''VideoGame/FinalFantasyVII'' can transform into a variety of monstrous forms using his limit breaks. Possible forms include Frankenstein's Monster, [[AxCrazy Jason Voorhees]] and Chaos, the BigBad of the first game in the series.
** [[VideoGame/FinalFantasyVI Terra]]'s Esper form seems to be this in ''VideoGame/DissidiaFinalFantasy'', as when she goes into it during the plot, she suddenly loses control and ends up fighting the other heroes.
* Django, the gun-slinging hero of ''VideoGame/{{Boktai}}''. In the second game of the series Django is infected with vampirism and almost loses his soul before his half-brother Sabata purifies him with the Solar Pile. After this, Django eventually gains the ability to transform between human "Red Django" and vampire "Black Django." Though it might be argued that Black Django isn't that much more powerful as, despite his dark-based powers, he loses the ability to use all of Django's magic (gaining new spells only he can use) and is harmed by both rain and sunshine. In the third game, the transformation is changed to a "Trance" attack, where he becomes much more powerful, however the transformation only lasts a limited time, or until you leave the room.
* The Terror Mask in the ''VideoGame/{{Splatterhouse}}'' series embodies this trope, especially in ''Splatterhouse 3'' where its own personality, and its effect on Rick, become more apparent.
* Queen Arshtat Falenas in ''VideoGame/SuikodenV'' took the [[BlessedWithSuck Sun Rune]] into her to prevent it from falling into the "wrong hands." Ever since, she [[PurpleProse melodramatically rants]] and [[NoblewomansLaugh cackles authoritatively]] whenever her "divine rule" is threatened. Once, she even unleashed the Sun Rune, completely dessicating a lake and its nearby landscape and leaving her nearby subjects to die a wasting death. All in all, a Super-Powered Evil Side is a great way to balance TheHighQueen and her [[GodSaveUsFromTheQueen darker counterpart]], leading to a natural [[TheWomanWearingTheQueenlyMask aloof regality]].
* In ''VideoGame/TheWorldEndsWithYou'', the BonusBoss is the Noise form of [[spoiler:Hanekoma]], and since he ''really'' kills you if you lose, it can be seen as this. The fact that, during the fight, he [[spoiler: spews his human form's inspirational phrases like battle cries]] could show that he's not quite in control.
* Emil from ''VideoGame/TalesOfSymphonia: [[VideoGame/TalesOfSymphoniaDawnOfTheNewWorld Dawn of the New World]]'' has Ratatosk mode, where he morphs from a [[TheWoobie Woobie-ish]] NonActionGuy into an ur-badass AntiHero BloodKnight. [[spoiler:It's not so much that Ratatosk is Emil's Super-Powered Evil Side; instead, Emil is Ratatosk's NonActionGuy side.]]
* At one point in ''VideoGame/WildARMs2'', Ashley is transformed into some kind of zombie-like creature early on, but before he is taken completely, he makes it to the [[OnlyTheChosenMayWield Argetlahm]] and pulls it out -- this has the result of countering the demon within him with the good force of the sword, and the resulting combination is a badass black-armored-red-trimmed entity called Knight Blazer. He can't actually use it in battle until a few plot points later, but once he gains the ability, nearly every remaining boss fight in the game boils down to letting him transform in order to open up a can of whoop-ass. [[spoiler:At one point, in a moment of UnstoppableRage fueled by [[HeroicResolve a terrorist threatening his girlfriend]], Knight Blazer actually [[TookALevelInBadass takes another level in badass]] and transforms into a gold-armored knight with extra abilities that is that much more powerful. And then at the end of the game, the "demon" portion escapes Ashley's body and reveals itself to be the EldritchAbomination responsible for devastating the world centuries ago, Lord Blazer. This leaves Ashley with the holy sword. Guess who wins [[ThePowerOfFriendship the]] [[ThemeMusicPowerUp resulting]] [[SugarWiki/AwesomeMusic boss]] fight.]]
* The God of War Melqart in ''[[VideoGame/TearsToTiara2 Tears to Tiara 2]]'', who [[TheHero Hamil]] summons to take possession of his body by promising the blood and destruction of [[TheEmpire The Holy Empire]]. Ennead and Monomack describes the technique as going berserk. At the Ba'al festival, Melqart wipes out an entire squad of Golmes in one blow, [[AxCrazy fights without concern for collateral damage, laughs as he effortlessly deflects fire arrows of imperial soldiers, and forgets all about protecting Tart]] until she sings. Not that she was actually in any danger by that point.
* ''VideoGame/MegaManBattleNetwork 4'':
** If [=MegaMan=] turns dark enough from the use of Dark Chips, his dark side will appear after he is K.O.'d and start fighting. [=MegaMan=] regains control after a while.
** The fight against Dark Rock in ''Battle Network 4'' does the same, using every chip the player had ever used, including Navi summon chips and Giga Chips, and also can use all the Program Advances you've performed up to the point you fight it. Unlike the player version, there's no warning when it uses them.
** Chaos Shadow Soul in ''Battle Network 5'' makes [=MegaMan=] completely invincible and uncontrollable as the AI attempts to duplicate the player's fighting style.
* ''VideoGame/TheSuffering'' initially plays this straight with a "primal form" that shreds enemies but damages your KarmaMeter. However, it's subverted twice over. First, you learn that [[spoiler:you're merely "under the delusion" that you turn into a monster when you go berserk]]. Then, the final boss proposes to "cure you"--and it sort of works. In the sequel, you can transform without harm, even if you're playing as a good guy.
* The Fierce Deity Mask ("Oni Mask" in Japan) in ''VideoGame/TheLegendOfZeldaMajorasMask'' turns Link from [[http://images5.fanpop.com/image/photos/32000000/Young-Link-Majora-s-Mask-the-legend-of-zelda-32057969-420-630.jpg this]] into [[http://img2.wikia.nocookie.net/__cb20100124002042/zelda/images/2/2a/Fierce_Deity_Link.png this]]. It's given to Link by (a representation of) [[BigBad Majora's Mask]] itself so they can play a twisted game of tag. The mask is such a GameBreaker that you're only allowed to use it in boss rooms.
* ''VideoGame/LegendOfMana'' has [[spoiler:the Mana Goddess]].
* ''VideoGame/EpicBattleFantasy 4'' has this for each member of the party as {{Bonus Boss}}es in [[BrutalBonusLevel Battle Mountain]].
* In ''VideoGame/{{Painkiller}}'', when you collect 66 souls of enemies you killed, you transform into an unstoppable demonic killing machine. It only lasts for about 30 seconds but that's all the time you'll need to obliterate an area full of monsters just by ''looking'' at them.
* It may not be on quite the same level, but in ''VideoGame/PokemonColosseum'', there's a random chance that a Shadow Pokémon might go into 'Hyper Mode' during a battle. The Pokémon in question will be surrounded by a black aura, and will do more damage - BUT. It won't be able to use any moves you've unlocked, it can't be healed, and it will also take recoil damage when it attacks. Thankfully, you can [[SayMyName call out to it]], which brings it back to its senses.
** A truer example would be Hoopa in ''VideoGame/PokemonXAndY'' and ''[[VideoGame/PokemonRubyAndSapphire Pokémon Omega Ruby and Alpha Sapphire]]'', who has a compact "Confined" form and a monstrous "Unbound" form where its Psychic/Ghost typing changes to Psychic/Dark. The "Evil" part is more prevalent in the film ''Anime/PokemonHoopaAndTheClashOfAges'', where the Unbound side becomes an EnemyWithout.
* Playable characters Dante, Lucia, Nero, Vergil [[spoiler:and Trish]] from the ''Franchise/DevilMayCry'' series all can transform into a demonic version of themselves with stronger attacks and health regeneration. In ''Devil May Cry 2'' this becomes [[ItsEasySoItSucks easy]], with the characters' demon forms not being thrown back, halted or even slowed by enemy attacks.
* In ''Franchise/StarWars: VideoGame/TheForceUnleashed: Ultimate Sith Edition'', you go into the ruins of the Jedi temple and eventually fight your Super-Powered Evil Side.
* Dark Spyro in ''VideoGame/TheLegendOfSpyro'' series is ExactlyWhatItSaysOnTheTin; Spyro's eyes turn white and his body gets covered in a flowing dark energy ([[ScrappyMechanic that has a habit of clouding up the camera when gliding]]) and gives Spyro the [[GameBreaker fury element]]. It gets triggered when Spyro is overwhelmed in sadness, anger, or just a plain ol' HeroicBSOD. However, in ''The Eternal Night'' you can flicker it on and off at will in NewGamePlus ([[ChangingClothesIsAFreeAction even in cutscenes!]]). He's shown to mostly have control over it though, as seen in ''Dawn of the Dragon''.
* Ryu from ''VideoGame/BreathOfFire 3'' can transform into the ultimate dragon, Kaiser. Its normal form ([[spoiler:the Infinity gene alone]]) is uncontrollable and Ryu will attack randomly (including his allies). Two other gene fusions allow it to be controlled, with one ([[spoiler:Infinity + Failure]]) significantly weaker than the "true" form ([[spoiler:Infinity + Trance + Radiance]]).
** Rei can transform into a weretiger after some story progression; like Kaiser, Rei's attack power is vastly increased but he attacks random targets. He can be directed to the target of the Influence skill (learned from Boss Goblins).
** Any character who uses the Berserk skill gains a similar effect as the weretiger transformation, but the downside is [[SuperPowerMeltdown that it kills you in three turns]] unless you have equipment that averts death.
* Every single main character in ''VideoGame/{{Persona 4}}'' must be recruited by defeating their Super-Powered Evil Side, or more accurately, their ShadowArchetype: the embodiment of all the things about themselves they can't stand to admit. The shadows have grown immensely powerful out of all proportion simply because being denied makes them stronger; once accepted, they become much weaker and "tame."
** The series also gives us Black Frost-the horrific result of adorable MascotMook Jack Frost remembering he's supposed to be a demon after all and invoking ThePowerOfHate. The process apparently renders him awesomely more powerful... and much more evil.
*** Unless you're playing ''VideoGame/DevilSurvivor'', in which case it turns him into a [[PungeonMaster Pun-spewing]] {{Magical Girl}}-esque [[ForGreatJustice warrior of love and justice]]. ...And just as awesomely powerful.
** ''VideoGame/Persona5'' has the traitor. Every Persona-using character has a costume which appears on their body when they enter the Metaverse. [[spoiler:The traitor has ''two''. One is a campy outfit styled after a "hero of justice", which he wears when summoning Robin Hood. This form has all the normal powers of a Persona-user. Should he switch to his other Persona, Loki, he'll change into a black, armoured outfit which adds a neck brace and helmet to the magical masks. This form has some abilities which most Persona-users definitely do not have, like inducing psychosis in a target and amplifying attack power massively in exchange for a defence drop. He's also a lot more open about how sadistic and angry he is when in this form, culminating in him using his powers on ''himself'' so that he can tear the protagonist apart with no remorse.]]
* ''Franchise/SpiderMan'':
** As said in comics, any game that has the option of the black suit has it as this. In games such as ''Spider-Man 3'' and ''VideoGame/SpiderManWebOfShadows'', his attacks become more violent and aggressive, usually with CombatTentacles and spike tendrils.
** Subverted in ''VideoGame/SpiderManShatteredDimensions'': the Ultimate Universe Spidey (who is bonded with the symbiote again) is the kindest of the Spideys, though he possesses a "rage mode" in which he becomes more scary looking and his attacks are more devastating. His comments are actually the opposite, however, and he'll say things like "Yeah, let's have some good old fashioned RAGE!" and "Raaage! I'm not actually angry, I just like saying it." But it's justified, since Madame Web is using her powers to keep the suit from taking over.
* This is the reason the [[UglyCute quaggan]] have survived in the PostApocalyptic world of ''VideoGame/GuildWars2'' despite being {{Actual Pacifist}}s; actually manage to piss them off, and they turn into what is best described as a cross between an orca and a [[TabletopGame/DungeonsAndDragons bulette]], with absolutely no regard for their safety or collateral damage. And when they calm down, they'll apologize for it.
* ''VideoGame/BlazBlue'': Mu-12, [[RedBaron the Sword of the Godslayer Kusanagi]], is this for [[TheCutie Noel]] [[ArtificialHuman Vermillion]]. In a twist of the usual formula, Mu is her ''original'' form, created to destroy Master Unit Amaterasu, the equivalent of ''God'' in this setting. A botching of her "smelting" process (as in the entire building and city she was in exploded) resulted in her being incomplete and developing her own personality. [[BigBad Terumi]] [[StrikeMeDownWithAllOfYourHatred invokes her transformation]] and completes the process, but she's saved by [[TheHero Ragna]] and later turns to tap into that power as a regular SuperMode.
* Hawke from the ''VideoGame/DragonAgeII'' "Destiny" trailer exhibits this, gaining RedEyesTakeWarning when he resorts to Blood Magic to CurbStompBattle the Arishok.
** Similarly, any time a Mage Hawke uses Blood Magic in-game, it could be seen as tapping into this.
** Anders has one in the Spirit of Justice, constantly having to fight to maintain control after his own anger corrupted it into a Demon of Vengeance. When he loses control, he gains GlowingEyesOfDoom, a [[EvilSoundsDeep Booming voice]], VolcanicVeins and a BattleAura.
* To an extent [[spoiler: Berserker Asura]] in ''VideoGame/AsurasWrath'' is this, and is also a OneWingedAngel transformation: It's something of a ShoutOut to the ''Manga/{{Naruto}}'' example above, as well as the VideoGame/DotHackGU movie's B-ST form. It helps that the guys that made ''Asura's Wrath'' make Franchise/DotHack and the Naruto Ultimate Ninja games.
* In ''VideoGame/PuyoPuyo Fever'', Klug has one in Strange Klug and Sig might have one in Black Sig. But we do mean "Super-Powered" for Strange Klug; he's not only a final boss, but some kind of demon king from long ago. He appears often due to, surprise, [[AssholeVictim Klug's]] AesopAmnesia of carrying a possessed book ''[[TooDumbToLive after it already possessed him.]]''
* ''VideoGame/{{Neptunia}}'':
** Noire and Vert, when they activate HDD. The Lastationian CPU becomes more brash and competitive upon transformation, while the Leanboxian CPU gets more arrogant.
** Ditto for Plutia in ''VideoGame/HyperdimensionNeptuniaVictory'', who become a full-blown sadist as Iris Heart who has no issues harming ''[[FriendOrFoe anybody]]'' physically, emotionally or ''[[BlackComedyRape sexually]]''.
* The hero of ''VideoGame/ShiningTears'' is normally a timid amnesiac with a dislike for fighting, but when somebody else puts on the other matching ring of power he turns into two super-powered sides, one is a moral knight of justice while the other is an insane OmnicidalManiac BloodKnight.
* In ''VideoGame/MetalGearRisingRevengeance'', Raiden recovers from a devastating HeroicBSOD by tapping into his "Jack the Ripper" ChildSoldier personality, turning him into an AxCrazy [[TheBerserker berserker]] who takes joy in inflicting pain. After the ensuing fight, Raiden can use [[SuperMode Ripper Mode]] whenever his Blade Gauge is full, increasing his attack power at the cost of constant Blade Gauge drain.
%%* A major plot point of ''VideoGame/{{Spellbreaker}}''
%%* [[spoiler: Chizuru]] has one in ''VideoGame/{{Aquapazza}}''.
* Happens sometimes in the ''VideoGame/FireEmblem'' series.
** Lyon in ''VideoGame/FireEmblemTheSacredStones'' gains this as a result of tapping into the Dark Stone, in Ephraim's route. (In Eirika's route, the power within the Dark Stone outright [[DemonicPossession possesses]] him.)
** General Gawain [[spoiler: aka Ike and Mist's father Greil]] in ''[[VideoGame/FireEmblemTellius Fire Emblem: Path of Radiance]]'' was already the strongest swordsman in Tellius before he took up the Fire Emblem; afterwards, it made him outright unstoppable, and uncontrollably bloodthirsty, until his wife [[spoiler: Elena]] sacrificed herself to pull the Fire Emblem out of his hand.
* In ''VideoGame/DragonBallXenoverse'', the villains Towa and Demigra have the power to bestow a dark power-up (officially dubbed "Villainous Mode") as part of their attempts to alter history. Most of they time they give it to characters who are already evil, but this trope is played straight the few times they inflict it on the heroes. The most prominent example comes near the end of the game when Demigra takes control Future Trunks thinking that the hero won't be able to hurt his/her own friend; Trunks maintains enough control to ask you not to hold back.
* In ''VideoGame/AvengersAcademy'', Superior Iron Man is interpreted as this for Tony. He goes mad with power after one of Loki's spells goes awry.
* In ''VideoGame/FalloutNewVegas'' we have Lily, a Nightkin who used to be a kindly old grandma before being mutated into a hulking blue monster. For the most part, she still acts like her old self, but all Nightkin suffer from schizophrenia. Lily's manifests as "Leo", a being only Lily can see who tells her to do bad things. If Lily is taken down to a quarter of her health, Leo will take over and go on a murderous rampage until every enemy in the area is dead. After witnessing this once, you can learn that she has been only taking half-doses of her medication because it makes the memories of her old life fuzzy. You can convince her to take a full dose (which will stop Leo's rampages but give her a drop in stats), or go off her meds entirely (which will boost her stats but make Leo come out at ''half'' health).
* The Abomination in ''VideoGame/DarkestDungeon'' is a [[OurWerewolvesAreDifferent werewolf]] that has mutated even his human form into a HumanoidAbomination, but the character in question is afraid that "it" does things behind his back such as eating children or causing mayhem and lives in constant paranoia as a result.
* ''VideoGame/TowerOfFortune'': The protagonist automatically transforms into a hulking, angry giant at 100% rage, with an 80% chance to hit (as opposed to the usual 45-65% range) and vicious, bloodthristy attacks from punching to sonic-screaming to pouncing on them and ripping their throats out with each subsequent hit. You can abstain from this mode with some skills or prolong the fury with others. How and why your otherwise generic warrior can become a were-giant is a mystery explained in the prequels.
* In ''Franchise/TheElderScrolls'' spin-off DungeonCrawler game ''Battlespire'', this is a trait of the Dark Seducers. Also known as Mazken, Dark Seducers are an intelligent race of [[OurDemonsAreDifferent lesser Daedra]] typically found in service to the [[OurGodsAreDifferent Daedric Prince]] [[MadGod Sheogorath]]. They are [[DarkIsNotEvil more humble and sympathetic toward mortals]], having less of a PunyEarthlings attitude toward them than most lesser Daedra. However, they are also known to [[IFightForTheStrongestSide Fight For The Strongest Side]], quickly switching allegiances if it becomes beneficial to them. The group of Dark Seducers fought in ''Battlespire'' betrayed their former master (a lieutenant of [[TheSacredDarkness Nocturnal]]) to side with BigBad [[DestroyerDeity Mehrunes Dagon]] when he promised them greater power. They were rewarded by being remade in the image of Dagon's own greed and treachery - becoming not only physically stronger, but also gifted with [[SuperMode powerful]] [[GoodWingsEvilWings bat-winged]] [[WingedHumanoid forms]]. In later appearances, they lack this form, but are still powerful and intelligent lesser Daedra akin to [[LegionsOfHell Dremora]] and [[LightIsNotGood Golden Saints]].

[[folder:Visual Novels]]
* Many characters in the Franchise/{{Nasuverse}} have an "inversion impulse", the desire to go psycho and unleash the full power their bitchin' superpowers on the world in an orgy of murder, due to their monstorous bloodlines.
** The BigBad in the ''VisualNovel/{{Tsukihime}}'' fighting game ''VideoGame/MeltyBlood'' uses his powers to summon {{Doppelganger}}s of several characters superpowered evil sides, leading to characters fighting their dark halfs; probably the biggest example being Nanaya Shiki, the evil murderous side of Tohno Shiki from the original VN.
** In the Heaven's Feel route of ''VisualNovel/FateStayNight'', [[spoiler:Sakura Matou]] lets loose a Super-Powered Evil Side powerful enough to kill most of the other participants and create a Super-Powered Evil Side of [[spoiler:Saber]].
* ''VisualNovel/AkaiIto'': Tsuzura's [[DevourTheDragon fox-mage]] mode. It's even played as what-do-you-mean-it's-not-rape the first time she taps into it and can't control it.
** ''VisualNovel/AoiShiro'': All who wield the <<Sword>> are prone to this, but Sword-Demon Kaya (your BackFromTheDead [[CameBackWrong Rather Wrongly]] big-sister-figure) especially... leading to a lot of NightmareFuel BadEnding.
* ''VisualNovel/HatofulBoyfriend'' has, during Anghel's endgame, a [[GenreShift boss fight]] with Himnesia, which looks like a GiantSpaceFleaFromNowhere. But dissect the things Anghel says there and elsewhere, and other characters' motivations, and official art, and some fans [[http://lexlee20.tumblr.com/post/23616979639/omg-himnesia come to the conclusion]] that Himnesia is his evil side. [[spoiler: And that he's a representation of the plague implanted in Anghel.]]
* '''VisualNovel/DRAMAticalMurder'':
** Aoba Seragaki has the ability to control other people and enter their minds [[CompellingVoice with his voice alone]] but the more he uses this ability, the more a darker, more powerful side of him that wants to destroy everything in its path threatens to consume him completely. [[spoiler:In the True Ending, though, it's revealed that his "evil" side was actually more lonely and misunderstood than evil and happily remerges with Aoba after Aoba fully remembers and accepts him.]]
** [[spoiler: Aoba's potential LoveInterest Koujaku]] turns out to have one as well. [[spoiler: His {{Power Tattoo}}s cause him to go into a massive UnstoppableRage in the Bad Ending, reducing his mind to a bestial state.]] This is also what caused [[spoiler: the death of his family when he was younger.]]

[[folder:Web Animation]]
* ''Machinima/RedVsBlue'':
** A fairly goofy example occurs in episode 40: in order to fight off a horde of "noobs" in Battle Creek, Caboose gets in touch with his "angry side", which results in him gunning down the noobs while shouting bizarre threats like "I will eat your unhappiness!" and "Your toast has been burned, and no amount of scraping will remove the black parts!"
--->'''Caboose:''' Now I'm thinking of a kitten... covered in spikes... that makes... me... angry... YYAAARRRRGGHHH!\\
''[Caboose jumps off the roof he was hiding on, shaking the ground when he lands]''\\
'''Caboose:''' My name is Micheal J Caboose, and [[PunctuatedForEmphasis I. Hate. Babies]]!\\
'''Red Zealot:''' It's the beast! The Anti-Flag! Come to live among us and rule for seven years! The end is nigh-- blleergh!
** He did this by replicating the effects of being possessed by the AI O'Malley, who gives whoever he inhabits a Super-Flanderized evil side, which in Tex's case makes her super aggressive. When he inhabited Grif he wanted to Take Over The World, but was too lazy to do anything. Only Church is immune to this effect, being as cynical as it is possible to be already. [[CerebusRetcon Among such reasons as]] [[spoiler: Omega being the embodiment of Church's rage. Church already has a HairTriggerTemper, but the Omega personality was formed back when he had lost his wife, and was JumpingOffTheSlipperySlope in remorse. When Church is seen after producing Omega in a flashback, he's little more than an EmptyShell who doesn't even remember her.]] The main villain of the series [[spoiler:embodies Omega's rage too, having originated them, and the evil he does is on a far grander scale than anyone else]].
* Shandala in ''WebAnimation/BrokenSaints'' has [[BreakTheCutie some]] [[BewareTheNiceOnes serious]] [[NightmareFuel issues]].
* Flippy of ''WebAnimation/HappyTreeFriends'' subverts this. Whenever he's reminded of the war he served in (strongly implied to be the Vietnam War), his SplitPersonality appears and starts gleefully and efficently killing everyone around him. However, the episode "Double Whammy Part II" reveals that the good side is just as badass, to the point where he manages to [[spoiler:(temporarily) kill the evil side]]. He just doesn't have a reason to utilise these skills most of the time, lacking the evil side's bloodthirst.
* ''WebAnimation/{{Dreamscape}}'': Keela's released form, which gives her BlackEyesOfCrazy, her scythe grows HUGE, and she turns totally evil.

[[folder:Web Comics]]
* Roger in ''Webcomic/CollegeRoomiesFromHell''. Unleashing his werecoyote side is often the Roomies' only way out of a tight spot, but he has trouble controlling it, and he's been warned by another werecoyote that sooner or later he'll be unable to change back. He actually has a second werecoyote form that is a stronger embodiment of this trope.
* Graveyard Greg of the ''Gaming Guardians'' has two separate and unrelated evil sides. Not only is he a werewolf, with an animalistic but self-aware wolf personality, but he's also possessed by a voodoo spirit which can take control of him at times. Greg has retained control by pitting them against each other, until they decided to team up to suppress him, becoming a zombie wolfman which calls itself "Mange".
* ''Webcomic/LastRes0rt'' has Jigsaw, since apparently [[OurVampiresAreDifferent all vampires in her galaxy]] can transform during their UnstoppableRage.
* In ''Webcomic/{{Jack|DavidHopkins}}'', the eponymous character, a personification of the sin of Wrath and the Grim Reaper, will occasionally enter a kind of "Wrath Mode". In this state, he will be overcome by his sin and gain a boost of power. He later [[spoiler:absorbs and seals the sin of Lust, who talks to him, hassles him and will sometimes help him in fights through his cloak.]]
* While "Fallen Grace" (a.k.a. "Dark Omega Grace") from ''Webcomic/ElGoonishShive'' falls much closer to the CrouchingMoronHiddenBadass type, she still deserves mention here. Not only is Fallen Grace actually willing to use her shape-shifting powers as a weapon -- unlike the pacifistic (NOT TechnicalPacifist) Grace -- she's also got access to the Lespuko Spurs; special claws that retard healing, thus neutralizing the advantage of the HealingFactor. She's also got horns, HellishPupils, and [[SpikesOfVillainy a whole lotta spikes]].
* In ''Webcomic/{{Gnoph}}'', Will's symbiotic partner Lyss usually acts as a [[BondCreatures Bond Creature]]; but when he passes out and she takes full control of his body, she acts like an example of this trope, due to being AxCrazy and having no compunction against killing (or ''[[ImAHumanitarian eating]]'') humans.
* Subverted in ''Webcomic/TheOrderOfTheStick'': It initially looked like the comic was going down this path when Vaarsuvius made a [[DealWithTheDevil deal with three fiends]] in order to save the lives and souls of [[AmbiguousGender his/her]] family. Having successfully rescued them from a dragon, (s)he then proceeded to [[spoiler:use epic magic to slaughter as many as a quarter of the black dragons in existence, in what was widely held to be a MoralEventHorizon by the audience.]] The next strip reveals that, contrary to what the devils said earlier, the power-up had no effect on Vaarsuvius' ethics and that whatever atrocities (s)he just committed were all of his or her own doing. [[spoiler:The fiends had lied to her in order to induce a nocebo effect.]]
* ''Webcomic/EightBitTheater'':
** Black Mage encounters himself in the Castle of Ordeals, where the Light Warriors have to face symbolic representations of their own flaws. However, the only thing that could represent Black Mage's flaw (Pure Evil) was himself, [[http://www.nuklearpower.com/2005/10/18/episode-613-mirror-master/ as nothing else was evil enough.]] Then it turned out that even his own duplicate didn't quite represent some of the more evil things he'd done, which corrected itself as the real Black Mage ran through them by becoming even more evil (as well as powerful). He then absorbed his own evil and power back into himself, [[http://www.nuklearpower.com/2009/04/30/episode-1123-endgame/ eventually unleashing it to destroy four other incredibly evil beings]], whose own evil and power he then absorbed, giving him an evil aura as well as incredible magical power.
** Later [[spoiler:omniscient superwizard Sarda (a.k.a. The Omnipotent Jackass) has absorbed Black Mage's Super-Powered Evil Side]]. {{Lampshade|Hanging}}d thus:
--->'''[[spoiler:Sarda]]:''' Who ''knows'' what kind of sadistic and impossible stuff I'll do now.
* Trace Legacy of ''Webcomic/TwoKinds'' has one of these. Whenever he gets extraordinarily pissed off, his memories of his old life cause a person shift. However recent comics have seemed to show this side is merging with is current persona. (As the racist evil side is shown defending [[UsefulNotes/FurryFandom Keidran]], which is something only his normal persona would do.)
* Played with in ''Webcomic/{{Homestuck}}'': [[spoiler: both of Gamzee's personalities are AxCrazy [[OmnicidalManiac Omnicidal Maniacs]]. They're just kept [[SplitPersonalityMerge merged]] and stable due to Gamzee's addiction to sopor slime.]] Rose's temporary grimdark transformation may also count.
* [[spoiler:Franken]] from ''Webcomic/{{Noblesse}}'' slips back to his MadScientist persona when he unlocks his power, which allows him to curb stomp ''absolutely everyone''. His SlasherSmile has to be seen to believe it.
* In some of [[http://zeurel.deviantart.com/ Zeurel]]'s OriginalCharacterTournament entries such as WebOriginal/LawOfTalos and WebOriginal/EscapeFromNevara, Black Ace is this to Spoiler.
* In ''Webcomic/{{Goblins}},'' [[PropheticNames Dies Horribly]] has a magical, green arm that acts as a sort of EmpathicWeapon most of the time. But when Dies is severely threatened, the arm tends to take over his body and slaughter everything in the immediate vicinity in creatively gruesome ways.
* In ''Webcomic/{{Roommates}}'' Goblin King Jareth has one. Technically it's his original personality, but his love and gratitude for the girl he choose, the camaraderie he feels for his friends and his own desire to change makes him suppress it. Not that it helps much, even his "Good" side is an "easily entertained but frequently bored trickster" (great intentions but sucks in this whole good thing) the "Evil" one is an "amoral ruthless fae lord" (FourthWallObserver meets TheFatalist and his role in the story tends to be: Villain).
* In ''Webcomic/HazardsWake'', [[ShrinkingViolet Araceli]] has a superpowered [[BlackMagic dark side]] that is [[DarkIsNotEvil not necessarily evil]], but leads to [[OneHitKill overkill]] when it manifests.
* Used in ''Webcomic/{{Snowflame}}'': [[spoiler: Possessed by the OddJobGod Goddess of Cocaine, SnowFlame is the Super-Powered Evil Side of Fabian Orozco, a former drug trafficker.]]
* In ''Webcomic/AliceAndTheNightmare'', Alice is implied to have something like this - whenever she gets angry, her eyes start to glow and she spills red dust (sign of dream magic) around. It seems that the medicine she takes daily keeps it at bay.
* Demons in ''Webcomic/SlightlyDamned'' have a berserk form that they can change into which greatly increases their strength and power at the cost of being consumed by uncontrollable rage such that they attack everything they see (including themselves if they are alone) and usually causing them to die from exhaustion, so they only do this when they are likely to die anyway. Buwaro was born with a condition that causes him to go berserk involuntarily when he isn't asleep or wearing a special pendant.

[[folder:Web Original]]
* In ''Literature/TalesOfMU'', the side of Mackenzie that some fans have taken to calling Kenzie is two details off from being a textbook example of a Super-Powered Evil Side: First, Kenzie is triggered by hunger instead of desperation in battle. Second and more distancing, the closest thing to a superpower Kenzie has over normal Mack is ''[[LawfulStupid being willing to hurt people that are trying to kill her]]''.
* In the DCU role-playing universe of JLA Watchtower/DC Nation, [[BewareTheNiceOnes Fauna]], a sweet, quiet GranolaGirl shapeshifter has this problem if you [[BreakTheCutie push her too far]]. Also, the more complicated her shapeshifting or extensive the use of her other abilities, [[TheMindIsAPlaythingOfTheBody the more feral she becomes]].
* In the "Angry Video Game Fag" by [[Website/TheDeadHorseInterchange Ebeeto]], Ebeeto "transforms" into The Angry Video Game Fag whenever he is angered enough. The transformation comes complete with a video game inspired cutscene.
* [[WebVideo/TheSpoonyExperiment Spoony]] treats Dr. Insano as this in ''WebVideo/{{Kickassia}}''.
* In the ''Roleplay/GlobalGuardiansPBEMUniverse'', Josiah Brimstone is a skilled and powerful sorcerer, but when his spells are not enough, he can unleash his [[ExactlyWhatItSaysOnTheTin inner demon]] on the bad guys. The inner demon doesn't always stop at beating down the bad guys, though, so Brimstone is really reluctant to do this. Viviane von Klause, the "Witch of San Francisco" tries to avoid overusing her magical abilities because if she goes too far and pushes her magic too far, the ghost of her Satanist grandmother takes over for a little while.
* [[CameBackWrong Dark Nella]] from ''WebVideo/TheNostalgiaChick.'' Technically she's supposed to be a CosmicHorror possessing [[spoiler:a clone of]] [[BigFun Nella]], but one episode randomly has Nella start to turn evil again before the Chick forces her glasses back on.
* The NationsAsPeople series ''Polandball'' has Germany. Though Germany's normally depicted as an amicable StraightMan and elder statesman, when he gets really pissed (usually at Greece [[RippedFromTheHeadlines for not paying debts]] or [[ButtMonkey Poland]] [[UnpopularPopularCharacter for existing]]), he morphs into the Reichtangle, an enigmatic figure representing the German Empire. The Reichtangle is [[NonstandardCharacterDesign a rectangle where everyone else is a ball]], and usually appears saying "Guten tag" before murdering everyone else.

[[folder:Western Animation]]
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'':
** The central example of this in the show is Princess Luna, whose jealousy and bitterness (and according to WordOfGod, an inkling of dark magic) transformed her into the evil Nightmare Moon, bent on plunging the world into eternal night so that ponies would have to acknowledge her night's beauty whether they wanted to or not. She snaps out of it after a thousand years of isolation and [[CareBearStare a rainbow to the face]].
** The same thing happens to Rarity in the comics, making the "superpowered" bit all the more obvious as she is able (with some help) to provide a serious challenge to the rest of the cast put together.
** A dream sequence in "[[Recap/MyLittlePonyFriendshipIsMagicS7E10ARoyalProblem A Royal Problem]]" introduces Daybreaker, a hypothetical superpowered evil side for Princess Celestia. Unlike Nightmare Moon, the trigger for this transformation is stated to be Celestia realizing that she has the power to do whatever she wants whenever she wants, and all that's stopping her is her caring about others.
** Dragons are prone to greed, and the greedier they get, the bigger and stronger they get, which makes them even greedier. In "Secret of my Excess", a few extra gifts on his birthday awaken Spike's dragon greed, and he becomes a huge rampaging full-grown dragon taking everything he wants from Ponyville. [[spoiler:He snaps out of it when he is reminded of his moment of generosity earlier in the episode.]]
* ''WesternAnimation/TeenTitans'':
** A splashing of chemicals prompts good-natured vegetarian Beast Boy to turn into a surly, meat-chomping bad boy who later turns into an anthropomorphic wolfman that was capable of taking on the entire team (as well as another wolfman). Later it's explained that, instead of turning Beast Boy into an actual lycanthrope, the chemicals only unleashed what was already there (which makes no sense considering that [[spoiler: they also changed Adonis]]), and he's given an antidote so that he won't transform against his will. He once again manifests this hidden wild side in a battle against Slade, slicing through a number of his goons before Slade puts a stop to it with his own supercharged powers. Possible subversion: It's made quite clear that "Man-Beast" isn't evil, just a really powerful, rather intelligent animal. Like any animal, it becomes hostile when scared, but generally it keeps to its human form's wishes. Beast Boy still expresses concern that it's still inside him at the end of the episode. He does seem to have acquired a degree of control over it later on, though he rarely uses it. In its first appearance, though, the Beast is more like [[ComicBook/TheIncredibleHulk the Hulk]]--not evil, but uncontrollable, volatile, and dangerous.
** There's Raven's "Daddy Issues". Dr. Light should ''really'' have backed off like she told him.
* ''WesternAnimation/KimPossible'': Ron Stoppable is ordinarily a likable goof, but he's been zapped a couple of times with AppliedPhlebotinum with superpowered evil results. The first time, the device was malfunctioning and gave him a transfusion of Dr. Drakken's evil, turning him into the insane, fiendish, blue-skinned, cleverer-than-Drakken-by-a-long-shot "Zorpox the Conqueror." The second time, the device was a properly-working instant MirrorMoralityMachine. A lot of this comes from Ron actually being BrilliantButLazy and often needing some negative event (such as Kim being in danger) to motivate him; these devices remove the "lazy" part to make him inexplicably hyper-competent to the point of being slightly unnerving (enough to cow Shego into obedience) -- he mastered the art of having multiple plots within what may well have been hours of his conversion, and showed himself to be a serious, focused martial artist, at least the equal of Kim. Granted, he HAS had secret ninja training...
-->'''Hego''': What's wrong with [[{{Sidekick}} him]]?\\
'''Shego''': [[ThisIsGonnaSuck I think he's evil now.]]\\
'''Hego''': [[TemptingFate Oh. Well, how bad could that be?]]\\
'''Shego''': [[CrouchingMoronHiddenBadass You'd be surprised...]]
* ''Franchise/{{Transformers}}'':
** An AppliedPhlebotinum instance is Rhinox being turned into a Predacon in the ''WesternAnimation/BeastWars'' episode "Dark Designs". He's an ideal minion on the surface, but beneath it, he's cunning, capable, and extremely aggressive, quickly taking it upon himself to create chaos in a takeover bid, which almost works until Megatron applies ReversePolarity to the AppliedPhlebotinum just in time to keep Rhinox from finishing him off. Good thing for Megs that Evil Rhinox just had to [[EvilGloating gloat like any other bad guy would have, huh]]?
** Megatron clearly learned his lesson from his ill-fated attempt at turning Rhinox evil in ''Beast Wars''. [[spoiler: He placed a RestrainingBolt in Tankor that would immobilize him if he ever tried to directly attack Megatron.]]
** Another example involving Rhinox shows up in ''WesternAnimation/BeastMachines'' when it was revealed that [[spoiler:Tankor, TheBrute tank that had been hounding the Maximals all season was really Rhinox in a sort of BrainwashedAndCrazy situation. Sadly things got even worse after Optimus Primal freed him from Megatron's control and he turned against his former allies and started an EvilPlan to take over Cybertron.]]
** Some poor, misguided fools seem to have heard that [=G1=] Grimlock is capable of combining with the Dinobots to create "the Beast," a terrifying titan of destruction and primal rage. '''These people are damned liars.''' Or at least, weren't [[http://tfwiki.net/wiki/The_Beast_Within aware]] that the sheer suckitude of that StoryArc was so much that Unicron and the Autobots teamed up to [[CanonDiscontinuity wipe it from space and time]].
* A literal form of this is ''WesternAnimation/TheBatman'' version of Clayface. Just using his powers turns him insane and monstrous.
* In ''WesternAnimation/EarthwormJim'', whenever Jim's puppy sidekick Peter is injured, he turns into a hulking, ravenous mutant whose sole goal in life seems to be beating Jim to a pulp. In a joke inversion, Peter's EvilTwin is evil when "normal", but his psycho mutant form turns out to be ''good''.
* The 2006 revival of ''WesternAnimation/BikerMiceFromMars'' has Stoker turn into an insane rat-like beast called Stoker rat.
* An episode of ''WesternAnimation/MrMeaty'' had Parker (who is normally calm under pressure because he just blissfully takes all those insults people kept throwing at him in) turn into a Hulk-like monster due to being unable to hold all those insults in any longer.
* In an episode of ''The New Batman Adventures'' (the one after ''WesternAnimation/BatmanTheAnimatedSeries''), Batman inhales an anti-fear toxin made by the Scarecrow. As a result, Batman has no fear. NONE. Bruce Wayne (in disguise) infiltrates some facility and has to deal with a moat with an alligator minutes after being exposed. He walks through the moat, becoming completely submerged. While still under water, he sends the animal flying from the moat and continues on his merry way. This later worsens as he loses his fear of ''killing''...
* Distinctly more of an Superpowered Id than Evil Side, but WesternAnimation/{{Freakazoid}} is like this to mild-mannered nerd Dexter Douglas.
* Coop on ''WesternAnimation/YinYangYo''. In his regular form, he's weak and nerdy. However, when he's infused with [[BigBad The Night Master's]] power, he becomes a match for Yin and Yang. Later on, Yin also gets a evil side to her when some of the Night Master's power corrupts her.
* When audiences found ''WesternAnimation/InvaderZim'''s [[RobotBuddy GIR]] cute, the writers created an episode where Zim actually fixes him -- and he becomes suddenly destructive and hyper competent, determining the only way to conquer Earth is with Zim out of the picture...
* A flashback in episode 19 of ''WesternAnimation/GeneratorRex'' reveals that Rex can turn into a savage biomechanical GiantRobot Evo. One of the reasons White Knight is so hard on Rex is that he is afraid of Rex becoming that monster again. Rex himself has no clue he can do this thanks to his amnesia.
* In ''WesternAnimation/WinxClub'', Lord Darkar uses his dark magic to turn Bloom into her Superpowered Evil Side in the form of Dark Bloom, who is Bloom with a black version of her fairy outfit and demonic yellow eyes. And he does it twice with her in the second season. Once to have her ship off Alfea's Codex piece to him through his TeamPet Kerbog, and again to have her help him open the portal to Realix with the four Codex pieces where he can acquire the Ultimate Power. Both times had her turned back to normal in the end - for the first time, the impostor Professor Avalon used his wand to lift the spell, and for the second time, it was Prince Sky who changed her back through his words of kindness, especially his "I love you" line, after which she returns the Ultimate Power to its rightful place to Darkar's shock and dismay.
* One episode of ''WesternAnimation/XiaolinShowdown'' was about [[OurDragonsAreDifferent Dojo]] transforming into an evil monster and destroying everything in his path after Omi accidentally frees him from his cage.
* The Shadow Thief from ''[[WesternAnimation/JusticeLeague Justice League Unlimited]]'' was eventually revealed to be the Super-Powered Evil Side of Carter Hall, who subconsciously willed him into existence out of a desire for a villain for him to defeat. He later attempts to kill Franchise/GreenLantern so that Carter can be with Hawkgirl.
* In an episode of ''WesternAnimation/TheRealGhostbusters'', an accident causes Slimer to start turning into a huge, demonic, bestial version of himself that the heroes name "Big Green", who sort of becomes a type of SplitPersonality. Once they find out what happened, Egon manages to separate them into two ghosts, and then defeat Big Green without hurting Slimer.
* ''WesternAnimation/AdventureTime'' has the Ice King as an odd, somewhat tragic, and not-so-''evil'' example. It's not immediately apparent, but when his backstory is revealed it turns out he ''used to be'' a normal, sensitive guy who discovered an ancient crown that gave him magical powers which allowed him to survive TheEndOfTheWorldAsWeKnowIt. Unfortunately, it also drove him more and more insane each time he used it, until, by the time of the series, he's locked into his Crazy/Evil Side full-time and can only vaguely recall his own origins and who he used to be.
** The series also has Sweet P Trunks, the adoptive child of Tree Trunks and Mr. Pig. A humanoid kid who is huge in size and also happens to be [[BigBad The Lich]] after being turned into a human with the Blood of The Citadel's guardians. While Sweet P is innocent and loving as any child, The Lich is still somewhere inside him, and if he feels cornered and threatened, he ''will'' take over. [[MindRape The King of Ooo and Toronto learn this the hard way]].
* Mike of ''[[WesternAnimation/TotalDrama Total Drama Revenge of the Island]]'' has an extremely comical case of multiple personality disorder, then in ''Total Drama All-Stars'' it's revealed that he has a sinister, [[ComicBook/ScottPilgrim Matthew Patel]]-like personality named Mal (known as "[[TheDreaded The Malevolent One]]") that his other personalities have previously kept at bay. The question of whether Mike is their body's original personality or Mal is the original and Mike is Mal's HelplessGoodSide who took control is brought up, but not resolved.
* In ''WesternAnimation/DexHamiltonAlienEntomologist'', Zap can turn into a [[OneWingedAngel giant destructive bug]] [[ArtisticLicenceBiology if his DNA becomes unbalanced]].
* In ''WesternAnimation/TheAmazingWorldOfGumball'', the titular character gets two:
** In "The Flower", Gumball gets possessed by a physical manifestation of his own jealousy of seeing NiceGuy Leslie with his love interest Penny. [[SubvertedTrope Unfortunately, he doesn't get any smarter and he still retains Gumball's poor physical strength.]]
** In "The Name", when Gumball is told that his birth name is Zach, it results in Zach becoming his own person who tries to erase Gumball from their mind by [[InternalRetcon rewriting his memories of his greatest failures into victories]]. Subverted as Zach isn't ''that'' much more competent than [[LoserProtagonist Gumball]], just a heck of a lot more egotistical.
* ''WesternAnimation/{{Kaeloo}}'': Kaeloo's alternate form, Bad Kaeloo, who has SuperStrength and whose actions are beyond Kaeloo's conscious control.
* ''WesternAnimation/OKKOLetsBeHeroes'': KO's evil side is TKO, who is a BloodKnight that is a bit of an EmoTeen parody. He lapses into TKO when he feels helpless or angry.