Villains aren't ones to preach self control or restraint. They might understand and even use it to good effect, but in their blackest hearts they want to live it up and tear up the scenery... in this trope's case, literally.
A villain who is Drunk on the Dark Side will show how "Evil Feels Good", he has become a God and With Great Power Comes Great Insanity, releasing waves or bolts of dark power, or if they're powerful enough cause a deliberate "controlled" Super-Power Meltdown that can become a Sphere of Destruction.
The downside to this exercise in expressive megalomania is that it's equivalent to (and sometimes paired with) becoming a One-Winged Angel, meaning the villain has completely surrendered to The Corruption and is too far gone for the heroes to be able to save, and thus killing the villain becomes acceptable.
Compare Drunk with Power, when it's authority-based power that goes to one's head. See also Evil Is Hammy, in which simply being evil is what causes scenery-chewing, rather than being evil and powerful.
Contrast This Is Your Brain on Evil, where the villain's mental processes are equally affected, but not in a fun way. The drug metaphor sometimes breaks down here, as villains will start out experiencing This Is Your Brain on Evil, then proceed to become Drunk on the Dark Side when their humanity degrades to the point that they stop fighting it. (With drugs, you normally lead off with the carefree intoxication part, while the soul-crushing addiction part comes later.)
- Magical Project S: When Misao, normally a shy, timid girl, transforms into her evil magical self, she starts to do everything she couldn't in powerless form — and as Pixy Misa, she starts to sing about how powerful she is (she sings in the middle of the street, as everyone assumes a WTF expression) with hilarious results.
- Muska in Miyazaki's Castle in the Sky qualifies at the climactic events of the film when he takes control of Laputa's powers and both kills the general and his soldiers and destroys the army's battleship with an army of robots, gloating, "A superior being such as myself has only one optionburn them!"
- Nene in Blue Dragon does this when he absorbs the main characters' powers.
- Death Note: Light Yagami started out as a kid groomed for success. His dream was to join the police and assist his father, the Chief of Police. He then became the popular guy in high-school because he was smart, studious, and Bishōnen. He was even smart enough to be one of the top scoring high-school students in all of Japan! Then he found a Death Note...
- In Bleach, Tosen goes absolutely insane after he realizes his Resurreccion gives him eyesight. More than he already was, anyway.
- And Aizen has gone off the deep end as well, doing incredibly dickish things for no reason except that he can, and loses it not once, but twice, when Gin succeeds in killing him and when he discovers Ichigo's more powerful than him now. Yes, that's in the correct order.
- Mabashi, in the Bount arc, was so against sucking living souls that he actually had to be force-fed his first. Afterward he goes Ax-Crazy, burning through any sympathy we might have had very quickly.
- Kariya, the Bount leader, attacked his allies in Soul Society and had to be restrained by two of his followers.
- During the Paramount War in One Piece, Blackbeard stole the Tremor-Tremor Fruit from Whitebeard's body and goes off the rails, threatening to destroy the island of Marineford, kill everybody, etc. It takes the arrival of Shanks to sober him, but it's likely a temporary solution for now at that.
- In Record of Lodoss War, the evil magician Wagnard becomes even more megalomaniacal by the final episode, cackling with mad glee as he blasts at Parn and Ashram with his magic from his scepter until Ashram eventually kills him. Even so, he gets to have one last bit of scenery to chew on as he screams, "All Lodoss is doomed! Hahahahaha! Nothing will remain! NOTHING! Hahahahahahaha!"
- Note that this is a failure in adaptation. In the original novel his plans are much more thought out and getting killed is actually the last part of his plan, so he can be reborn into a lich. Performing the ritual to resurrect the demon god AND people stopping the ritual in the midst of it so the demon god does NOT get resurrected are both well written in his plans. This is understandable because when the anime is made, the novel is still not finished and the animators only had an outline to work with and there are way more characters involved in the novel that the shorter anime cannot implement.(Which made way to the sequel anime instead).
- Sasuke Uchiha from Naruto initially wants power to surpass his treacherous brother Itachi, but with time, he spirals dangerously out of control. Too much exposure to evil and Mind Rape twisted him into an Ax-Crazy lunatic — learning Itachi pretended to be a villain so his brother would kill him to atone for slaying his clan, but actually still loved him was what made him crack. Now, he's to the point where he wants his whole village wiped out. Unless... his revived brother can convince him otherwise...
- Turns out it just made him more convinced to destroy the village.
- But now, after having spoken with all four Reanimated Hokage brought back by Orochimaru, he's gone to help the Shinobi Alliance in the war, and even expressed a desire to become Hokage himself to stop the ninja system that ruined Itachi's life. What.
- And then it turns out that what he meant when he said that was that he was going to pull a Zero-Approval Gambit and get the ninja world to unite against him. He seals away the Tailed Beasts and the climactic fight of the series is Naruto beating some sense into him.
- Turns out it just made him more convinced to destroy the village.
- Cardfight!! Vanguard: Aichi Sendou goes from Shrinking Violet, Shy Blue Haired Guy protagonist to a (possibly) mentally unstable kid desperate to be acknowledged as strong once he's hooked on Psyqualia. So much so that he abandons the very card that means the world to him in favour of the clan's Evil Counterpart. He manages to get over it, but once he faces Ren, whose pretty much the same, Psyqualia takes hold again and even develops his own Evil Laugh.
- Seidou Takizawa has become that in the sequel/second part of Tokyo Ghoul. He's enjoying being so powerful, giving philosophical speeches to his captive audiences, cackling like a lunatic, taunting his prey with sing-songing nonsense, and is thrilled when the sound system gets activated meaning everyone can hear him gloat! Moderation and restraint do not seem to be in his vocabulary anymore.
- The villains of JoJo's Bizarre Adventure have a habit of going on a power trip just minutes before they're defeated.
- In Battle Tendency, Kars finally succeeds with his aspiration of becoming the Ultimate Life Form and goes on a Hamon-fueled rampage that's so extreme that he triggers an immense volcanic eruption that flings him out into space where none of his powers are able to save him and his immortality dooms him to drift through the empty void until the day he stops thinking.
- In Stardust Crusaders, DIO first stalls for time until the sun has set so the Joestars cannot exploit his vampiric weakness to sunlight. Then, after a Car Chase for shits and giggles, he becomes a No-Nonsense Nemesis, mercilessly killing Kakyoin by punching a hole straight through him and leaving Joseph on the brink of death with a knife through his neck. When he realizes that Jotaro has the same Time Stands Still powers as him, he ditches the straight-forward No-Nonsense stuff. And then... he drains Joseph's blood... and becomes so high on his newfound powers that he might as well have drained the Villain Ball...
- In Diamond is Unbreakable, Yoshikage Kira actually succeeds in killing off all of the heroes with his newfound unstoppable ability Killer Queen Bites the Dust. However, in his moment of victory, Kira gloats about his victory and identity out loud right before the heroes are fated to die, alerting Josuke to his vicinity and forcing him to release Bite the Dust and rely on his original Stand powers.
- By the end of Stone Ocean, Father Enrico Pucci slaughters all of the protagonists save Emporio, a young boy, and wipes them from existence to finally complete DIO's ultimate plan. By the time he confronts Emporio, he believes that he's completely won and there is nothing that can be done against him. This allows Emporio into tricking Pucci into inserting the Weather Report Stand Disc into his body and allows him to finally kill him.
- During the penultimate battle of Steel Ball Run, President Valentine believes himself to be complete invincible with his new D 4 C Love Train ability, and declares that he will use this power to redirect all misfortune for the United States onto foreign countries. This overconfidence allows Johnny to throw him off guard when manages to acquire a power that surpasses Love Train.
- Superboy-Prime, starting with Infinite Crisis and getting steadily worse thereafter.
- The Scarlet Witch in Avengers Disassembled and House of M. As of The Children's Crusade, she's fine again.
- Madelyne Pryor did this when she became the Goblyn Queen and tried to sacrifice her own son to usher in a Hell on Earth. Needless to say, though she's died and come back since then, she'll likely Never Live It Down.
- Hal Jordan after his temporary FaceHeel Turn and being possessed by Parallax.
- Happens in Mega Man, when Mega Man starts getting the Robot Masters' powers he starts to get increasingly cocky and arrogant, to the point where he declares himself invincible. This results in Dr. Light having to contain him while he throws what amounts to a super-powered temper tantrum. When he calms down, he's so horrified at his response that he asks Dr. Light to take them away.
- An act of Fridge Brilliance on the writer's part - this explains why Mega Man's acquired powers don't carry over into the next game - he's only borrowing them until Wily's beaten.
- In the original The Transformers comic book series by Marvel, this happens to Starscream after he absorbs power from a mysterious satellite called the Underbase and becomes so strong that he's able to take on the combined might of both the Autobots and Decepticons combined and curbstomp them both. He's only defeated when Optimus Prime tricks him into absorbing the rest of the Underbase's power, which turns out to be far too much for any single Transformer to hold.
- Every time Lex Luthor gains superpowers, he quickly lets them go to his head. His term as president came to an end when he went crazy after doping himself with Venom and liquid Kryptonite before going on a rampage in an Apokoliptian battle suit. In 52, he uses his own Exo-gene therapy to copy Superman's power set and spends most of the time reveling in his new powers. After temporarily wielding an Orange power ring in Blackest Night, Luthor spends most of his story in Action Comics trying to replace it with something equally or more powerful.
- Mary Marvel in Countdown to Final Crisis. So much so she goes evil twice.
- Magneto tends to become pretty hammy and nuts whenever he goes full throttle with his powers. Then again, he commands absolute power over one of the four fundamental forces of the universe. That would give just about anyone a rush. It's also been implied that his magnetism powers make him literally bipolar.
- In Disney's Aladdin, Jafar really hams it up after wishing to become the world's most powerful sorcerer and in his Laughing Mad moment after the Prince Ali Reprise, and when even that isn't enough, he wishes to become a genie himself and hams it up even more until he notices the BIG downside to being a genie.
- The Pagemaster:
Fantasy: Dr. Jekyll? Dr. J?Mr. Hyde: My name is MR. HYYYYYYDE!!!!
- Disney's Frozen has one with Anti-Villain Elsa when she realizes she can finally express her emotions in "Let It Go", below, boy does she ever rise to the occasion.
- My Little Pony: Equestria Girls:
- Sunset takes a few levels in psycho and hamminess when she finally gets the crown and is transformed by its magic. Prior to it, she was nasty but had some standards and operated on a more rational level. She confirms in Friendship Games that the power of the crown was so great that it overwhelmed her. The climactic fight with Midnight Sparkle has her able to control the magic she's using that time around, instead of this happening.
- This is pretty common in MLP G4 overall. Princess Luna also ramps up her (already considerable) hamminess as Nightmare Moon, and Midnight Sparkle takes a shy, awkward girl and turns her into someone who could give Darth Sidious a run for his money.
- Dungeons & Dragons (2000). Jeremy Irons hams it up as Profion at the climax so much, his skull is ready to pop out of his head.
Profion: LET THEIR BLOOD RAIN FROM THE SKYYYYYY!!!!
- In Iron Man Obadiah Stane, normally calm and Affably Evil, seems to lose his shit after becoming the Iron Monger, and even seems to realize it.
Stane: I have to admit, I'm deeply enjoying the suit!
- Galadriel in the Fellowship of the Ring film. "In place of a Dark Lord, YOU WOULD HAVE A QUEEN! Not dark, but beautiful and terrible as the dawn! Treacherous as the sea! Stronger than the foundations of the earth! ALL SHALL LOVE ME AND DESPAIR!" Slight subversion since she's testing herself against what she might become under the Ring's corruption. (It's much more subtle in the book.)
- Skeletor pulls one of these in the Masters of the Universe movie. Oddly enough, his godlike power does not allow him to win a swordfight against He-Man.
- Is it any wonder this is the actor's favorite role?
- Theodora dives into this trope headfirst in Oz: The Great and Powerful, so deeply that she even scares Evanora, who'd convinced her to become a Wicked Witch in the first place.
- Star Wars:
- Palpatine really tears into Mace Windu with the Force lightning in Revenge of the Sith. Also provides the now-iconic page quote.
- He later (In-Universe) pulls a repeat performance on Luke in Return of the Jedi.
- Being drunk on the Dark Side is considered a legitimate strategy among the Sith as a whole.
- It's part and parcel of a Sith's power in the first place — as opposed to the Jedi, who control the Force through serenity and self-discipline, a Sith unleashes it through raw, destructive emotion — and as such, even a normally self-controlled Sith like the Emperor will go straight to Large Ham mode when using his powers. Add to this the chronic justified paranoia about everyone around you due to their Chronic Backstabbing Disorder and Klingon Promotion as standard operating procedure. This also explains a lot as to why almost every Sith in the Star Wars Expanded Universe acts (and looks) like they snorted a mountain of cocaine (or, in-universe, spice).
- X-Men Film Series
- The Wolverine: When Ichirō starts to age back through sucking Wolverine's powers, he laughs like a lunatic.
- X-Men: Apocalypse: Professor X enters a deep trance when Apocalypse possesses his mind through Cerebro. Xavier is so overwhelmed and mesmerized by the plethora of god-like abilities that he comes into direct contact with ("I've never felt power like this before") that he initially doesn't resist the invasion, and he's temporarily corrupted by it (hence his Black Eyes of Evil). It's only when Hank tries to remove the Cerebro helmet that Charles snaps out of the daze (which results in him regaining his normal eye colour) and attempts to fight off his attacker. While under Apocalypse's control, Professor X is in a calm state (the drug-like high), but the moment he struggles to break free, he's constantly screaming in agony (the withdrawal)—Evil Feels Good, in other words, even for an All-Loving Hero like Xavier.
- Most Let's Play videos of Garry's Mod Murder involve this to an extent, although most of these examples are not taken entirely seriously. Many examples below:
- From Hat Films, Ross Hornby will pull out the knife with no warning, shouting EAT SHIT! EAT SHIT! or some amusing variation thereupon at the top of his lungs. His two co-stars do this on occasion, but Ross is by far more noticeable.
- Turpster is considerably better than Ross at hiding that he is the murderer, but upon being discovered he puts on a creepy voice and gives a brilliant Evil Laugh.
- Lewis Brindley and Simon Lane rarely delve into this, but when they opt to, they can be very hammy, funny and terrifying all at once. The former goes on a gangster-style rampage (audio file NSFW with lots of swearing and profanity), complete with a EastEnders impression. The latter learns not to do it after his first attempt at doing so gives him away and gets him killed, but later does it for comedy, at one point going on a hammy rampage which can be heard here (also very NSFW due to constant swearing, and you would be advised to turn your volume down).
- During series 2 of the Yogscast playthrough of Trouble in Terrorist Town, the guys are mostly savvy enough to avert this, but in the final episode, Lewis Brindley embraces this trope. After a small firefight which results in the deaths of Sips and Sjin, Lewis initially tries to deny that he is responsible for their deaths, but upon further probing he hammily confesses, then guns down Ross and Trott, ranting about how he had to kill and boasting as he does so. Sjin puts it down to Demonic Possession.
Simon Lane: What the fuck is going on?Lewis: Die, all of you! EAT SHIT! EAT SHIT! I'm possessed!Sjin: (helplessly laughing) Ross has somehow possessed Lewis!
- Strippin is normally composed enough, albeit slightly boisterous, but during a playthrough of Damned with In The Little Wood, Rythian and Zoey Proasheck, he shows he's Not So Above It All, with Creepy Child impersonations and sadistically toying with the others.
- Annals of the Western Shore: In Gifts, the Caspro family legend of Blind Caddard ends this way. Although he learned to control his power, in his old age he starts unmaking anything and everything that pisses him off even slightly. He eventually has a Heel Realization and uses a mirror to unmake his own eyes.
- Dreamblood Duology: Because dreamblood is highly addictive, once a Gatherer kills on purpose and without being welcomed, he becomes a Reaper and requieres a constant supply of dreamblood. And he will kill anyone who comes close enough to get it.
- In The Dresden Files wizards who use Black Magic tend toward this. The magic subtly warps the wizard's mind so they'll want to use it again, and each usage warps them more until all traces of morality, and often sanity, are gone. Case in point; Molly Carpenter used magic to force her friends to quit using drugs, unwittingly damaging their minds and souls in the process. Thanks to that, she's now constantly tempted by the prospect of magically reading or manipulating people's minds in order to get results. There's a reason breaking any of the Laws Of Magic is a big freakin' deal.
- Dresden has had to deal with this for most of his life ever since he killed his Evil Mentor in self-defense when he was a teenager. His struggles with not using magic against some foes reads a lot like an addict fighting the need for a fix. Various supernatural beings offering him more power like a bunch of drug-pushers don't help matters any.
- The Enchantment Emporium has sorcerers, who turn out to be male members of the Gale family. It's believed that if one starts out with enough power, this trope is inevitable, and a preemptive strike on any found would save the world a lot of hurt.
- A side-plot is Allie trying to save her older brother David, by trying to show how his rumored power can be used for good, in her battle against Samuel Gale, the most recent one to get away.
- Nicolae Carpathia in the Left Behind books was like this when Satan indwelt him after his "resurrection" to fulfill his role as the Antichrist — so much that, at the battle of Armageddon, Satan temporarily departs to tell Nicolae that he's getting too big for his britches!
- Tends to happen in the Shannara books whenever magic is overused, most obviously in the backstories of the Warlock Lord (who got turned from Well-Intentioned Extremist to power-mad tyrant), the Mord Wraiths (who got turned into near-mindless puppets of the sentient Tome of Eldritch Lore known as the Ildatch) and the Shadowen (who became addicted to magic and fed themselves by leeching it out of both individuals and the Earth as a whole). The Warlock Lord is particularly hammy about it, too ("MORTAL CREATURE, I AM HERE!"), and many Shadowen are as well when dropping their mortal guises; the Mord Wraiths don't really talk, but demonstrate extreme arrogance and obsessive devotion to their beloved book nonetheless.
- Star Wars Legends:
- In The Wheel of Time, the Dark One provides its greatest servants the True Power, an Evil Counterpart to the One Power that fuels the setting's magic. Using it is described as equal parts agony, ecstasy, and sheer omnipotence; it's also supremely addictive and causes major Sanity Slippage, to the extent that the one person to use it regularly ended up believing that he was the Dark One.
- In the Buffy the Vampire Slayer episode "Revelations", renegade Watcher Gwendolyn Post tricks the Scooby Gang into recovering the evil artifact the Glove of Myhnegon, and promptly becomes this trope.
after Miss Post has put on the Glove of Myhnegon and absorbed its powerFaith: What's going on?Ms. Post: Faith... a word of advice: you're an idiot!blasts Faith with lightning bolt
- Charmed: Phoebe, in the S6 episode "Witch Wars", where she gets a crap-ton of demonic powers and promptly goes on a demon murder spree. And she enjoys it. Of course, she had been going though active power withdrawal for some time and it was completely awesome but you can kind of see why the Powers That Be depowered her in the first place...
- Doctor Who: The Master in "The End of Time". He gets resurrected, is constantly hungry (to the point where he devour an entire turkey in mere seconds), transforms nearly every human on Earth into a clone of himself (which gets undone via Reset Button), keeps talking about the drums in his head, has many (more than usual) homoerotic moments with the Doctor, and is last seen attacking Rassilon, the Lord President of the Time Lords while chewing all of the scenery in sight, right before he gets pulled into the Last Great Time War with the other Time Lords and Gallifrey.
- In Earthsea, after Ged experiments with shapeshifting into a sparrowhawk during his one-upmanship war with Jasper, Archmage Nemmerl warns the student body off of shapeshifting. He tells a tale of a wizard who liked shapeshifting into a bear so much that he gradually forgot he was originally human, killed his own son in bear form, and was finally hunted and killed by villagers.
- Once Upon a Time: The longer Rumplestiltskin has his powers, the worse he gets, especially after he loses his Morality Pet son. (While Mr. Gold, Rumple's depowered human Storybrooke counterpart, remembers who he is, he is much calmer and in control of himself than his fairy tale self.)
- Supernatural At the end of season six and the beginning of season seven, this has happened to Castiel after he absorbed all the souls in Purgatory to gain the power to prevent Archangel Raphael from restarting the Apocalypse—although it's hard to tell exactly how much, since he's been increasingly like this all season. His relationships with everyone became rocky partly because his friends can all be jerks, partly because he was growing distant and inhuman, and mostly because he became ruthlessly practical and overly focused on his cause even before absorbing too much monster-soul power. He gave a whole Villain Speech to Dean, tortured an innocent woman to death for her blood, murdered a close friend (Balthazar) for telling the Winchesters where to find him to stop him, broke Sam's mind as a distraction, and chose to work with Crowley over Dean in the first place.
- Only after accessing the tainted power does Castiel proclaim himself a new god and threaten his friends' lives. In season seven, Dean's fears and continued willingness to kill Castiel are borne out by Castiel smiting angels and humans even before the voracious Eldritch Abominations inside him tip him into a murderous rampage and he nearly explodes before the unkillable monsters escape into the world.
- Supergirl: Several times, ordinary people who gain powers end up liking them so much, they don't mind the price they have to pay or the harm they cause. Dr. Grace Parker became disillusioned with life, believing that goodness was never rewarded. So when the personality and powers of Pestilence awoke within her, she eagerly accepted them, even being willing to kill her personality to be killed by Pestilence in order to obtain true power! Thief Pamela Ferrer becomes host to an alien symbiote called Menagerie, which eats hearts to stay alive. Pamela enjoys the enhanced strength and other abilities granted by Menagerie, which allows her to steal anything she wants, while gleefully allowing Menagerie to rip hearts out of people's rib cages.
- After Shantae completes the Dynamo machine in Half-Genie Hero, it infects her with dark magic instead of destroying it. Turns out Risky Boots knew Shantae would complete the plans, and tricked Shantae into getting the wrong blueprints from her. Nega-Shantae promptly tries infecting all of Scuttle Town with dark magic. Luckily, Bolo, Sky, Rottytops and Uncle Mimic all pull Shantae back from the brink with The Power of Friendship.
"I know what you can do... You can suffer! You can squirm like the pathetic maggots you are! Wallow in torment and pain forever in oblivion! Now beg! Beg for your very lives!"
- In Knights of the Old Republic, most of the students at the Sith Academy have this to various degrees. In fact, one way to get inside is to murder one such student, since he's just being a total dick and killing people at random because he cant get over how easy it is. If you turn to the Dark Side, you can force one of the main characters to kill his best friend because she won't swear loyalty to you. Although he'll snap out of it and turn on you if you keep him in your party.
- In Sa Ga Frontier, Asellus, a half-Mystic, can enhance and develop her Mystic abilities with three specific pieces of equipment. Developing them grants her more powerful skills and enhances her abilities when she uses Mystic Change, but she becomes more tyrannical and power-thirsty at the same time. In the ending where she becomes a full Mystic (which is done by fully developing her powers with all three of the mentioned equipment pieces), she turns out to be an even worse tyrant than Orlouge (the Mystic overlord before her) ever was. On the other extreme, not developing her Mystic powers at all will allow her to become a human again.
- Final Fantasy villains are fond of this trope, coupled with nihilism. To name a couple, Kefka, and Kuja.
Kefka: I've tapped into the ultimate power. Observe...! Such magnificent power! You are like insects to me!
- Kefka is a subversion, as his personality stays exactly the same after gaining ultimate power - which is bad, because he was a gleefully psychotic monster to begin with. Kefka goes from being a gleefully psychotic man to being a gleefully psychotic god.
- Esher in Myst V: End of Ages does this if you make the mistake of giving him the tablet.
- The reason the "canisters" in Geneforge are listed under both Upgrade Artifact and Psycho Serum—not only are they addictive, they're prone to causing egomania, severe anger management problems, Hallucinations, and, occasionally, Body Horror.
- Exposure to Phazon causes this in the Metroid Prime Trilogy. In the third installment, Samus gets to experience it herself. It's still better than the alternative, though.
- In Mega Man Zero 2, as the final boss Elpizo is transforming into his One-Winged Angel form, he lets out a piercing scream, and then yells (in Japanese) "MORE POWER!!!" in a demonically distorted voice.
- In the Demon Path of Soul Nomad & the World Eaters, Revya does this, intoning "More... More power..." during some attacks, complete with a Voice of the Legion.
- In Overlord II, when you drain Queen Fay of her magic, she slowly begins to be corrupted by your dark magic, begging for you to continue and yelling at the Elves and Pixies for trying to save her. By the end she's driven completely insane and becomes a full-on Fallen Hero who joins you.
- In the Kingdom Hearts series, Ansem Xehanort and Organization XIII are so Drunk on the Dark Side that sometimes it seems like the darkness is all they ever talk about. This even gets a Lampshade Hanging in Kingdom Hearts 3D: Dream Drop Distance. It's to the point where only Riku has managed to use the power of darkness without falling into corruption; even Terra paid dearly for it in the end.
- Space Channel 5: "Ulala! I needed your dance power you see, now we have all the power we need!"
- In World of Warcraft:
- It is a quite common effect of demonic magic, especially for careless users. One boss in Magister's Terrace which, after charging up with a bit of it outright screams "YES! I AM A GOD!". His boss, Kael'thas, gets "unlimited power"-style quotes in both his appearances.
- In a meta vein, whenever any class or skill ends up buffed up significantly, players of that class will go on this trope completely. In one case, Shamans getting the ability to cast Chain Lightning with no pauses made the resulting light-show look just like Palpatine's Force Lightning. Flooding of Youtube with mashups of his quote from the page top with in-game footage promptly followed.
- This is one of the more... legitimate reasons Blood Magic and dealing with spirits is forbidden for mages in Dragon Age.
- Most of the voice acting in the first Baten Kaitos game is very wooden and monotone. However, during Kalas' FaceHeel Turn...
- In Odin Sphere, the spell of Darkova transforms its user into a powerful three headed demon beast. The user is then cursed with a thirst for blood and pain, compelling them to destroy that which they love most.
- Albedo from Xenosaga firing Proto Merkabah at Second Miltia is an example of this.
- Racing Lagoon has Kyoji Nanba, the nicest guy you'll ever meet in the game, ends up looking like a zombie and speaking brokenly after he has taken drug and driven a monster-tuned car. Right after that, he drives straight into a barrier and gets himself killed.
- On something of a meta level, it is not uncommon for players of Garry's Mod Murder to devolve into a psychotic, screaming berserker if they are discovered to be the murderer. This does end up working against them if they are not careful, since a careless murderer may start screaming violent threats and fail to notice that they've left a large group of people alone.
- Street Fighter: Whereas Akuma uses the Satsui no Hadou (Surge of Murderous Intent) as a Dangerous Forbidden Technique while trying to keep the more negative tendencies of its use in check, Evil Ryu doesn't care and draws on it as much as possible, turning him a vindictively arrogant at best and outright murderous at worst Blood Knight. Oni is what would become of Akuma if he was as unrestrained as Evil Ryu when it comes to using the Satsui no Hadou and he is far worse about it than Evil Ryu ever was (promising nothing short of an Omnicidal Maniac-level outcome).
- WarioWare Gold involves another one of Wario's schemes to get money. This time, it's hosting the Wario Bowl tournament. The player is one of the many competitors. Towards the end, Wario reveals the Wario Bowl was a scam for a prize that will never come, and uses the pot to turn into Wario Deluxe, plunging the world into darkness while announcing that the power is explosive before confronting the player in a final showdown, during which he cheats and uses lightning to hide the control schemes for four microgames. Luckily, the player is still able to beat Wario Deluxe after Lulu comes in to assist.
- In Endstone, rocking the Banestone does this.
- In Homestuck Rose Lalonde does this after going Grimdark
- Yeager in Nodwick acted this way when he had won the power of "The Quirkening", going so far as to threaten to kill Nodwick... well, ok, he's normally like that, but this time he meant to use his Reality Warper powers to really screw him over.
- Vaarsuvius in The Order of the Stick, after making a Deal with the Devil. At least initially. Soon after the character starts actually using that power, they feel nothing but frustration as resolutions to some plot threads have been reached without having them use it. And then finally when they try to fight the Big Bad, an Evil Sorceror that technically has less power, but is more than equal and is much more proficient in its use where it matters, they get stomped and lose all of that power. Though while the end result was far short of what the character imagined, they still managed to achieve a couple important things - and could have done more if not for the power-drunk rampage.
- In Sinfest, Slick notes that the successful treated patients at the Hellness Center are crazy.
- Chloe in Eerie Cuties, when she found a demonic Amplifier Artifact made for mature succubi — which she isn't. She quickly grows powerful and restless, sliding out of control and from an innocent crush to rather crazy to full demoning-out with urges to corrupt pretty quickly, ending with a breakdown and then a bad hangover after the "fun" ends.
- Sarda in 8-Bit Theater, episode 1171: "In fact, I didn't think it was possible, but now I hate you even more! The super powered evil I absorbed from Black Mage seems to be responsible. Who knows what kind of sadistic and impossible stuff I'll do now."
- From The Dungeons And The Dragons, a group of D & D players have invited one of their mothers to sit in on a game to prove that roleplaying games aren't evil like Jack Chick says. It turns out that it's she herself who turns evil. We're talking The Exorcist on steroids evil.
- Dreamscape: Soon after training under Melinda, Melissa saw knowledge as a sign of power, instead of a sign of enlightenment. She used her knowledge of The Dark Arts to carry out Melinda's evil bidding, but luckily Dylan and Alice gave her a change of heart.
- RWBY: Cinder's desire is to become strong, feared and powerful and she works for Salem because it gives her the opportunity to steal Maiden powers. While she only possesses half the Fall Maiden's power, she is able to execute Salem's plan for the destruction of Beacon Academy with great cunning, patience and adaptability, and obtains the Fall Maiden's full power. While recovering from injuries inflicted by Ruby, she becomes increasingly intolerant of Salem's measured approach to pursuing her goals and is warned by Salem to wait patiently for further power. Once unleashed to lead the infiltration of Haven Academy, Cinder's leadership becomes increasingly unstable. She revels in bullying others by flaunting her Maiden power and she watches the Spring Maiden's demonstration of power with an expression of undisguised lust; when Raven concludes that Cinder is egomaniacal, Watts agrees. Cinder sacrifices caution and stealth for the chance to confront Ruby and uses the first opportunity she gets to try and steal the Spring Maiden's power for herself, revealing in the process that she's replaced her left arm with a Grimm arm that makes it easier for her to steal Maiden powers. As a result of her obsession, lack of patience and growing lust for power, she ruins Salem's plan; Haven Academy is rescued, the villains are forced to flee, and Cinder is cast into a bottomless abyss by the Spring Maiden.
- In the Whateley Universe there is an explicit mental illness that makes one more susceptible to this, Quinzel-Osborn Syndrome, though it is something that can happen to almost anyone under the wrong circumstances. Apparently, it is often seen in conjunction with Deidrick's Syndrome, Hercules Syndrome, or certain expressions of Galahad Syndrome, which only ups the insanity quotient all around.
- Self-proclaimed Phoenix King Ozai from Avatar: The Last Airbender acts this way when Sozin's Comet comes into close orbit with the planet:
"I have all the power in the WOOOOOOOOOOOORRRRRLD!!!"
- In the Season 2 finale of Justice League Unlimited, Lex Luthor becomes this way after merging with Brainiac. He mentions that in that state, he has power, and he likes it. Throughout season 3, he constantly tries to reactivate Brainiac from a small piece of technology-covered rock to regain that feeling.
- My Little Pony: Friendship Is Magic: This happened with Trixie while wearing the Alicorn Amulet in the season 3 episode "Magic Duel". She was a pretty Large Ham to begin with, and the Amulet not only drastically increased her power but corrupted her mind. In this case, it's reversible because all it takes is removing the Amulet and giving her a bit of time to come off the high.
- In Skeleton Warriors, Baron Dark can turn anyone the least bit corruptible into a Skeleton Warrior with a touch. The Skeleton Warriors really enjoy being unkillable undead monstrosities. So much so that at the end of one episode, two of Dark's henchpeople who had their humanity restored beg him to turn them into Skeleton Warriors again.