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-> ''"I'm saying... I'm saying I'm an insect who dreamt he was a man and loved it... but now the dream is over, and the insect is awake."''
-->-- '''Seth Brundle''', ''Film/TheFly1986''

After months or years of suffering a SplitPersonality, EnemyWithin, or SuperPoweredEvilSide, the character is cured! ...by having the weaker, "sane" personality lose all control over the body to their inner evil. Like the slow erosion of a mountain, [[JekyllAndHyde Jekyll]] has succumbed to [[JekyllAndHyde Hyde]]'s [[ImplacableMan implacable]] [[PassionIsEvil id-like force]], leaving nothing but the shell of who they were.

This isn't just an [[SecretIdentityIdentity identity crisis]] or something [[IKnowYouAreInThereSomewhereFight that can be wished away with good intentions]], at least [[BattleInTheCenterOfTheMind not easily.]] This is the permanent and [[LiteralMetaphor literal]] [[ThatManIsDead death of a person]]-- or at least a personality.

This is especially common if one personality is [[GollumMadeMeDoIt more dominant than the other]], or the "good" personality is subject to MindRape or a HeroicBSOD. Occasionally, a truly strong willed "good" personality can do the takeover-- although it's likelier that they'll choose to [[SplitPersonalityMerge "merge" or reintegrate]] with their evil side into a "whole" personality because GoodIsImpotent.

If the takeover is incomplete, expect to see signs that the original is FightingFromTheInside. Antonym to SplitPersonalityMerge. When this is induced by outside brainwashing, it may be BrainwashingForTheGreaterGood.



[[folder:Anime and Manga]]
* Subverted in ''Manga/AhMyGoddess''. Belldandy's sister, Urd, being half-demon and half-goddess, forcibly has her good and evil halves split apart by Mara, and when they are rejoined, she finds that her demonic side is slowly slipping away, which would eventually result in her becoming a full-blown goddess. However, Keiichi and her sisters refuse to let the Urd they've come to know disappear, so they summon the only person other than the Almighty One (whom they assume won't help them since he would rather Urd become a total goddess) with enough power to safely return Urd to stable demon/angel form--the ruler of all demons and her mother, Hild. It works, but they accidentally end up convincing Hild to leave a portion of herself behind on Earth to torment them along with Mara.
* Subverted in ''Anime/AngelBeats'', where Tenshi manages to win out against dozens, if not hundreds of murderous versions of herself after all of them [[SplitPersonalityMerge recombine into one person.]] Given her exhausted state when it happened, and Key's tendency to KickTheDog, it was a close call.
* A variation occurs in ''Manga/ElfenLied'' as [[spoiler:Lucy's good personality takes over the evil (if [[TheWoobie tragic and even pitiful]]) one but neither personality is okay with the {{omnicidal maniac}} side taking over at the end of the manga, leading to a {{shoot the dog}} moment from Kouta.]]
* In ''Anime/{{Animerica}}'', this occurs to [[spoiler: Kiyone, explaining his MagnificentBastard actions in Season 2. The "evil" side attempts to do this again in the beginning of Season 3, but thankfully it gets destroyed for good this time.]]
* ''Anime/{{Trigun}}'':
** [[spoiler: Knives Millions]]'s short transition from a hugely caring and even oversensitive cute boy to a [[TheWoobie Woobie]] who hides a lot of anguish and anger management issues from his loved ones to [[spoiler: the friggin' biggest homicidal psycho in Gunsmoke's short history and the responsible of what's probably the biggest genocide in human history, period]]. The anime [[AdaptationDecay arguably oversimplifies his transformation and motivations]], making his FreudianExcuse quite ludicrous.
** The manga also suggests that [[spoiler: Legato Bluesummers]]' original personality may have been pretty ordinary and that he used to have normal human needs, but that it soon got twisted beyond recognition by years of horrifying abuse in a small town plagued by criminality (and pedophiles) in the middle of nowhere-in-{{Mordor}} and [[spoiler: not even having a name, parents, or a past worth mentioning in his view]].
%%** It also nearly happens to [[spoiler: Livio in the manga]].
%%* Happens to The Count in ''Anime/{{Gankutsuou}}'', who can almost claim without lying that ThatManIsDead.
* In ''Manga/SaintSeiya'', the BigBad of the first major plot arc is Saga, Gemini Gold Saint, a saintly (forgive the pun) warrior in Athena's service, whose SplitPersonality is thoroughly and irredeemably evil. Naturally, it takes over for good, which results in the Sanctuary War, although Saga's good side still shows occasionally (if only to have an HeroicBSOD at his own actions.)
* This is why Moka never takes off the rosary herself in ''Manga/RosarioToVampire'': the outer Moka would be replaced by the inner Moka forever. [[spoiler:This doesn't stop her from trying it anyway.]]
* Marik and Dark Marik from ''Anime/YuGiOh''. The split personality was born when Marik's father carved his back. The pain was so severe that Marik created a second masochistic personality to cope with it. Dark Marik took control to [[spoiler:kill his father]] a year later and intended to [[spoiler:do away with the rest of the family]], but he retreated back into Marik's subconscious due to his MoralityChain adoptive brother, Rishid (Odion in the anime dub). When Rishid falls unconscious, Dark Marik takes control and [[spoiler:nearly succeeds in killing Marik for ownership of his body]].
* ''Manga/{{Bleach}}'': Hollow transformations consist of the original personality being largely destroyed in favour of something created from raw instinct. The effect is permanent; even if a hollow can resist the effect (such as Sora), it's only a temporary measure at best. The effect ''does'' lessen as a Hollow goes through its stages of evolution and their personality reverts closer to their original as their never-ending hunger becomes sated (Adjuchas and Vasto Lorde level, as well as becoming an Arrancar), but that takes a long time and a ''lot'' of devoured creatures to get to. The exception is Ichigo who did eventually learn how to control his hollow power and in the final arc it's revealed [[spoiler: to be the basis for his shinigami power and his zanpakutou's sealed form]].
* Goes the less common direction for [[spoiler: Riff]] in Manga/CountCain, who [[spoiler: was given a nice personality in order to gain Cain's trust, which then faces off, and wins, against the original evil one.]]
* ''Anime/PrettySammy'' quotes this trope to Misao which it encourages her to help her in getting rid of Ramia's evil influence over her.
--> ''Even if you stay as Pixy Misa forever, I'll still really love you, Misao!''
* In ''Manga/{{Psyren}}'' when Amamiya is shot [[spoiler: Abyss, her other personality created from her suppressed emotions takes over momentarily.]]
* Played with in ''Manga/SamuraiDeeperKyo''. In the manga version, Demon Eyes Kyo is a legendary killer whose mind has been sealed inside the body of Mibu Kyoshiro, but occasionally rises to the surface. In the anime version, Demon Eyes Kyo is the dark side of Kyo's personality that escaped and became an EnemyWithout, then was reabsorbed back into Kyo. In both versions, Kyo eventually assumes full-time control of Kyoshiro's body.
* ''Manga/InuYasha'':
** Although [[BigBad Naraku]] already dominates Onigumo, he plans on removing his heart from him since his love for Kikyo prevents him from hurting her.
** A more classic example comes from Inuyasha himself: whenever in the presence of a powerful demonic aura and/or separated from his sword [[RestrainingBolt Tessaiga]], his demon blood takes him over and he transforms into his fully demonic form, then proceeds to wantonly murder anyone nearby. It takes an increasingly large amount of effort to bring him back to normal each time.
* ''Manga/FullMetalAlchemist'':
** [[spoiler:Bradley's body's original owner was bound to a Philospher's Stone and waged a war with the various personalities trapped inside the Stone until the current Bradley became dominant. Even he's not sure whether he's the original test subject or some other personality.]]
** Averted with [[spoiler: Ling/Greed]], which started off this way but ended up as more a case of SymbioticPossession.
%%* ''{{Manga/Berserk}}'': This is the {{Hellhound}} [[EnemyWithin Beast's]] ultimate intention with [[TheCorruptible his host]] Guts.
* [[spoiler:Shiro]] in ''Anime/DeadmanWonderland'' seems to have had her violent side take over. [[spoiler:[[WhamEpisode Chapter 55]], however, reveals that this is Averted, as her supposed SplitPersonality never existed in the first place. She is incredibly jealous of Ganta for being able to live a comfortable life she never had as a result of being his replacement and was doing everything in her power to make sure he was strong enough to kill her.]]
* In ''Manga/WChange'', the heroine is a sweet airheaded girl who has an incredibly violent persona that surfaces whenever she falls unconscious. Halfway through the series, her "dark side" took over as her main personality.

[[folder:Comic Books]]
* In Creator/FrankMiller's ''ComicBook/BatmanTheDarkKnightReturns'', Harvey Dent has received surgery to repair his face's damaged half, but it has the opposite effect on his mind - Two-Face is now entirely in control.
%%* Michael Moran does this to himself in Creator/AlanMoore's run of ''{{Comicbook/Miracleman}}''.
* There's a ''Franchise/SpiderMan'' arc involving Symbiote knockoffs. ComicBook/{{Venom}}, of course, always refers to himself as 'We' (as in, Eddie Brock and his Symbiote), so when one of the symbiotes stops talking in plural, Spidey knows that she's all gone - the Symbiote has taken over her mind. An interesting conclusion of this is that the very thing that makes Venom sound like a raving lunatic is actually an indication of his remaining sanity - or even a psychic crutch necessary for him to retain his identity.
* While it wasn't made as big a deal of as the animated version, it used to be that the Goblin Serum gave ComicBook/NormanOsborn a SplitPersonality, and would periodically forget he had a SuperpoweredEvilSide and go back to being an industrialist. Since he came BackFromTheDead, it seems to be accepted that he's the Goblin all the time. Though during his time on ''Thunderbolts'' and ''Dark Reign'', it seems the split personality explanation is back. Subverted in that Osborn is still an evil jerk, the Goblin is just his darker side. At the end of "Goblin War", [[spoiler: the Goblin formula is flushed from his system, and he declares that Spider-Man has never faced a Green Goblin who's ''sane'' before...]]
* What caused Brainwave's initial FaceHeelTurn after the end of ''ComicBook/InfinityInc'' About fifteen years later, [[EnemyWithin the new personality]] got possessed by [[PuppeteerParasite a ''third'', also villainous, personality]]. Eventually, when the third personality was defeated, it was heavily implied that the third personality ''ate'' the second one. In any case, [[HeelFaceTurn he got better]].
%%* A horribly tragic case occurred to Dan Turpin during ''ComicBook/FinalCrisis''. To be fair it skirts between this and DemonicPossession, but after visiting Bludhaven in search for missing children, Danny starts getting blackouts and finds he can't control himself after a certain point. He then discovers with horror that he is being '''possessed and/or erased''' by [[{{A God Am I}} Darkseid]]. After he is completely possessed, he is poisoned by Batman, nearly killed by the Black Racer, and finally and utterly destroyed by Superman.
%%** The final issue implies, but never outright states, that it was only Darkseid who got destroyed and Turpin was ultimately freed. It's probably a moot point now that DC has reset the universe again.
* Inverted, to some extent, with [[Comicbook/IncredibleHulk the Hulk's]] son Skaar, where the weaker, more vulnerable personality ('puny' Skaar) has recently managed to escape Skaar's suppression of him in their shared mind.
* ComicBook/BettyRoss was in constant risk of this when she was Red She-Hulk.
* During the ''Comicbook/SpiderMan'' storyline ''The Gauntlet'', [[spoiler: Curt Connors']] worst fears are realized when [[spoiler: he loses a battle of wills with the Lizard part of his psyche]]. [[spoiler: The Lizard kills and ''eats'' Curt's ''son'' Billy, and "Curt" essentially dies due to the trauma, leaving only The Lizard]]. A later story reverses this [[spoiler: Spider-Man manages to bring Curt's body back, but doesn't realise it's still the Lizard's mind. Then the Lizard reverts to his usual form, but ''this'' restores Curt's mind. Curt keeps this quiet because he feels he ''deserves'' to be locked up.]]
* This was Bloody Mary[=/=]Typhoid Mary's (a villainess most often found in ''Comicbook/{{Daredevil}}'') entire schtick. She had rather impressive psychic and telekinetic powers, but she also had a horrible case of multiple personality disorder; namely, at least nine of them. Two of them (the aforementioned Bloody/Typhoid Marys) tended to take over more often than not, and there have been at least two instances where one or both have "permanently" taken over only for later events to unlock her original (non-powered) personality once more.
* Happened to [[ComicBook/UltimateMarvel Ultimate]] Comicbook/MoonKnight. Doubles as a case of BecomingTheMask, since the personality that took over was created specifically to be more evil and violent.
%%* ''ComicBook/{{Etrigan}}'': This has happened to Jason Blood from time to time, depending on who's writing the Demon.
* In Golden Age DC comics, Priscilla Rich's jealousy and envy of ComicBook/WonderWoman caused her to spawn a second personality. As the Cheetah, she became a recurrent foe in the Sensation Comics and Wonder Woman series.

[[folder:Fan Works]]
* ''Fanfic/PonyPOVSeries'':
** Discord originally entered the mortal world [[AmnesiacDissonance as an innocent version of himself named Dissy]] who had none of his evil self's memories. Sadly, Discord's original persona still existed and eventually began to awake until it finally devoured Dissy and began his thousand year reign. It's mentioned in-universe this happening was unique to Discord, as most deities instead have a SplitPersonalityMerge in situations such as this. [[spoiler:However, later it turns out Dissy still exists and begins to resurface during the Rumors Arc to aid the heroes.]]
** A benevolent version happens with [[spoiler:Minuette, who's actually [[Series/DoctorWho the Master]] using a fob watch.]] While her evil persona spends the arc attempting this trope, eventually [[spoiler:Minuette manages to destroy the Master by feeding his fob watch to the [[ClockRoaches Blank Wolf]], allowing her to take his place fully.]]
* The dark side of Socrates attempts this in ''Fanfic/CalvinAndHobbesTheSeries'', as his transmitter chip has fused with his mind, allowing the dark version to try and take over the land inside his head. The protagonists stop him, of course.

[[folder:Films -- Live-Action]]
%%* The ending of the movie ''Film/{{Identity}}''.
%%* Happens to [[spoiler: Clark Stevens ]] at the last part of ''Film/{{Madhouse2004}}''
%%* ''Film/{{Psycho}}''. "Why, she wouldn't even harm a fly..."
* In the remake ''Film/TheFly1986'' Scientist Seth Brundle slowly transforms into a pathetic and diseased human-fly hybrid after accidentally fusing with said-insect in a teleporting experiment. At first, the deformities were purely physical, as his human flesh warped and decayed into a "cocoon" under which the monster grew. Sadly, he also transformed on a mental level into an instinct based animal, unbound by compassion and morality. The love of Veronica, our heroine, was sadly not enough to stop his predictions from coming true...
* Averted in the sequel ''Film/TheFlyII'' with Brundle and Veronica's son Martin. The murderous rampage against his oppressors is all him, as shown where he actually goes out his way to avoid harming a dog and sparing his LoveInterest Beth Logan, implying that his mind has largely remained unchanged despite his body's transformation. Said oppressors are bad enough that this isn't a MoralEventHorizon for Martin.
%%* Similar to ''Film/HideAndSeek'' where [[spoiler: Charlie completely takes over David.]]
%%* ''Film/FightClub''. Claimed by [[spoiler: Tyler Durden]] to be the evil plan all along.
* [[VeryLooselyBasedOnATrueStory The VERY heavily fictionalised]] film of "The Boston Strangler" implies something like this at the end. The killer, Albert De Salvo, has been diagnosed with Multiple Personality Disorder (the real life De Salvo was never even suspected of having this condition,) and the film ends with him apparently having gone permanently catatonic after re-enacting one of the murders under the influence of his murderous side, and with no sign of the gentle family man left.
%% * Phoenix in ''Film/XMenTheLastStand''.
* In the "Ventriloquist's Story" in ''Film/DeadOfNight'', ventriloquist Maxwell Frere (Creator/MichaelRedgrave) smashes up his puppet/DemonicDummy "Hugo" (who, it is strongly implied, channels Maxwell's own SplitPersonality) after "Hugo" tauntingly threatens to join Maxwell's rival ventriloquist. Maxwell is placed into a mental institution and goes into a catatonic state until his doctors bring in the rival ventriloquist to try and give him a jolt. Upon seeing the rival, Maxwell smiles and opens his mouth, but the voice that comes out of his throat (his lips remaining unmoving) is that of "Hugo".
* In ''Film/TheTwoFacesOfDrJekyll'', Hyde tries to enforce this by framing Jekyll for his crimes, knowing that the doctor will have to cede control to him lest he be a hunted fugitive.
* In ''Film/ThorRagnarok'', Bruce Banner fears that the Hulk is starting to do this. After [[Film/AvengersAgeOfUltron he had to transform to help fight Ultron]], Hulk maintained control of their body for ''two years'' while they were stuck on Sakaar, with Bruce being totally unaware of any time passage. When Thor notes that the team may need Hulk to take back Asgard, Bruce refuses the idea vigorously because he's not sure if he'll ever turn back again. [[spoiler: Ultimately he's forced to Hulk out in order to defeat [[CanisMajor Fenris]]. The movie leaves it ambiguous if a takeover has indeed happened or not, but the fact that Hulk doesn't turn back into Bruce once everybody's safe doesn't bode well...]]

* This happened to Dr. Jekyll at the end of his [[Literature/TheStrangeCaseOfDrJekyllAndMrHyde strange case]]. Luckily for Victorian England, Jekyll locked himself up before changing completely and ultimately [[TakingYouWithMe committed suicide]].
%%* Happens to some of the Clayborn in David Wingrove's ''Literature/ChungKuo'' series.
%%* In the Skulduggery Pleasant books, [[spoiler: Anton Shudder/his gist, Valkyrie/Darquesse and Skulduggery/Lord Vile]]. All of them double as SuperpoweredEvilSide.
* In a rare case of the good side taking over (with a little help), from Creator/GeneWolfe's story "The Death of Doctor Island", the psychotic teenager William, whose brain has been surgically divided between the left and right hemispheres, is deliberately subjected to a devastating trauma which leaves him catatonic. This allows his previously helpless right-brain personality, the calm and placid "Kenneth", to take control of his body.
%%* Happens to [[spoiler: Arnie Cunningham]] in ''Literature/{{Christine}}''.
* ''Literature/ArtemisFowl'':
** Happens in ''The Lost Colony'', when [[spoiler: after Artemis and Co. escape from the TimeCrash that's about to happen on Hybras, Qweffor (assisted by N°1) does it to the BigBad Abbot.]]
** Happens again in ''The Atlantis Complex''. Artemis, having the titular disease, is [[spoiler: taken over by his alter, Orion, multiple times.]]
* Happens to one of the bad guys in Shade's Children: [[spoiler:When the titular KnightTemplar VirtualGhost uploads himself into a supercomputer, his conscience becomes personified in Robert Ingman, who is, coincidentally, Shade's original identity. As with the trope, Robert eventually destroys his dark side and helps the protagonists banish the local {{Dimension Lord}}s. Too bad the [[RedemptionEqualsDeath other rule about redemption]] is played quite straight.]]
* In ''Literature/TheLordOfTheRings,'' the character Gollum's darker side of his personality ultimately ends up taking control over his kinder side.
* Came ''this close'' to happening to Tahiri/Riina from the Star Wars: New Jedi Order series. Riina was not "evil", ''per se''- though extremely messed up, she had a PetTheDog in one of the few times she actually did manage to seize control of their body, and the merge helped Tahiri regain her sanity largely because each compensated for the other's issues (Riina's acceptence of pain and death helped Tahiri get past her emotional fragility following her boyfriend's death, while Tahiri's moral center held back Riina's more violent urges).
* In ''Literature/ThePiloFamilyCircus'', this happens to every single [[MonsterClown clown]] employed by the circus, due to prolonged use of the magical facepaint they wear: it takes around two years of usage for the new personality to completely merge with the clown's brain, but since the facepaint also grants the user superhuman strength, a newly-recruited clown has to wear it just to survive the early months at the circus, and by then, the clown's addicted. Jamie, the novel's protagonist, only ''just'' manages to avoid this fate.
* This happened to a teenager named [[spoiler: Saxon Hyde]] at the beginning of Michael Slade's ''Ghoul''. That's especially unfortunate, because [[spoiler: Saxon was the only one of this young man's personalities that ''wasn't'' a serial killer.]]
* The first half of the ''Dragonlance: The New Adventures'' series consists of an evil wizard trying to engineer one of these. He implanted the preserved spirit of a powerful evil sorceress in one of his mindwiped servants to try to access her magical knowledge once she took over the servant. Needless to say, the sorceress is rather pissed when she does take over.
* In ''Literature/ZenAndTheArtOfMotorcycleMaintenance'' [[spoiler: the Narrator first tells us that Phaedrus has been killed by several thousand volts to the head. However, throughout the Chautauquas, it becomes clear that Phaedrus is alive and kicking and trying to gain control. Slightly different from the others, as it's the narrator's personality, the ''sane'' personality, that is the real takeover.]]
* In Creator/StephenKing's short story "Secret Window, Secret Garden," Mort Rainey's alter ego John Shooter claims Rainey "took the coward's way out". He briefly reverts to Rainey, but only after [[spoiler: being shot]].
** King likes this trope; the same effect befalls Jack Torrance in ''Literature/TheShining'' and the whole town of Haven in ''Literature/TheTommyknockers''.
* Creator/RobertLudlum's ''Literature/TheBourneSupremacy'' features the Jason Bourne persona forcibly suppressing the civillian identity, [[spoiler:David Webb]], whenever they need to focus on doing something that requires his particular skillset or way of thinking. [[spoiler:Later in the book, Bourne completely takes over as 'Delta', the insane version of David Webb that led Medusa into battles in Vietnam, in order to violently break into the sterile house. Fortunately Marie is there to bring Webb back to the surface.]]
--> [[spoiler: ''"David Webb had disappeared, only Jason Bourne remained. Yet he was both more and less the hunter of Carlos the Jackal. He was Delta the predator, the animal wanting only vengeance for a priceless part of his life that had been taken from him once again"'' ]]
* In ''Literature/FightClub'', the [[NoNameGiven Narrator]] spends the story slowly succumbing to his intense, charismatic dissociated identity [[DarkMessiah Tyler]] [[TheTylerDurden Durden]]. Ultimately, [[spoiler: the Narrator is DrivenToSuicide in order to stop him]].
* The FateWorseThanDeath of Olivia from ''Literature/HiveMind''. As a telepath, she had to deal with the people she read sticking in her mind. Most telepaths eventually figure out how to clear these "echo personalities" out, but she never did, so she ended up drowning under them; by the time she appears in the story, the original Olivia is essentially gone. [[spoiler:One of her new personalities has fully taken over and started a terrorist cell, hoping that the treatment once she/Olivia is found out will let her fully eject the original Olivia and other echos and be the only personality.]]

[[folder:Live-Action TV]]
* Played with in ''Series/{{Farscape}}''. Thanks to Scorpius' [[MoralityChip neuro chip]], Scorpius' "neural clone" gets stronger and stronger within Crichton over the course of the second season... until taking over completely in the finale. Even after surgery removes the chip itself, the neural clone, "[[NotSoImaginaryFriend Harvey]]", never really disappears.
** Once the chip is removed though Harvey loses any power he had and is basically trapped in John's head forever, with John able to shut him up whenever he wishes. The best Harvey can do to John is be mildly irritating - unless his life is in danger, in which case, Harvey can muster up ''just'' enough power to be dangerous. In the Peacekeeper Wars mini-series Harvey finally dies for good when the wormhole knowledge is deleted from John's brain.
%%*** We've heard that one before.
* Basically what happened to Talia in ''Series/BabylonFive''. There was also a rogue telepath in one episode that goes through this.
* Born vampires from ''Series/YoungDracula'' all go through an attempt at this when get their full vampire status. How strong-willed they are seems to determine how much of their original personality is left afterward.
* Implied to have happened at the end of a ''Series/{{Married With Children}}'' episode in which Bud's "cool" personality took over. It had absolutely no visible impact on future episodes (though perhaps that's the joke; Bud's so uncool that even his cool side is uncool).
* In an episode of ''Series/CriminalMinds'', a young man's murderous and until-then unknown alter-ego permanently takes over his body, in an attempt to protect him. In a twist, the alter-ego that took over was ''female''.
-->'''Dr. Reid:''' I am looking for Adam.
-->'''Amanda:''' Just because you caught me doesn't mean you'll find him. You're not that smart.
* ''Franchise/{{Stargate}}'':
** An episode of ''Series/StargateSG1'' had Daniel controlled by several different personalities that got in his head.
** ''Series/StargateAtlantis'' has an episode where Rodney and a (female) Marine wind up sharing his body. They each fight over control of the body, until it can't take their fighting anymore: if one of them doesn't give up and willingly disappear, both will die.
* ''Series/UnitedStatesOfTara'': Alice, the "housewife" personality, reveals that she's jockeying to be the emergent personality if Tara ever resumes therapy. This was followed by Bryce, Tara's alter based on her childhood abuser, revealing that he wants to "kill" Tara.
* ''{{Series/Jekyll}}'': When [[EvilInc Klein & Utterson]] finally manage to capture Dr. Jackman, they put him into a device that deletes one of the two personalities. Unfortunately for Jackman's wife, Hyde is the surviving personality. [[spoiler: However, when Mrs Jackman and her children are captured due to Hyde's immaturity, he resurrects his dead alter-ego and [[SplitPersonalityMerge merges]] with him, mixing Hyde's incredible strength with Jackman's maturity.]]
* This happened repeatedly to Nikki on ''{{Series/Heroes}}'' when her SuperpoweredEvilSide decided to start acting up.
* ''Franchise/{{Buffyverse}}'':
** This happens to Willow when [[spoiler: Tara]] dies.
** After [[ManchurianAgent Spike]] regains his soul, he intermittently becomes evil again after The First Evil prompts him with a Victorian folksong.
** In season 8, it's shown [[OurWerewolvesAreDifferent Oz]] came very close to going down this road ''willingly''. He had been trying to deal with [[EnemyWithin his werewolf side]] for a relatively long time, only to learn that whatever he tried was pointless and whatever ground he had gained before was lost. Eventually giving in and simply being ''done'' with it all started to look very tempting. It's never explicitly stated why he didn't go through with it, but [[TheStoic his words]] "But I didn't" are [[YouAreNotAlone coupled with an image of Bayarmaa]], [[spoiler: his future wife and mother of his son]].
** This happens to Angel whenever Angelus is unleashed.
* In ''Series/TerminatorTheSarahConnorChronicles'', [[RobotGirl Cameron]] experienced a case of this when her processors glitched due to combat damage, and Cameron slipped into an alternate personality mode that thought it was a woman named Allison Young, who was [[spoiler: a resistance fighter in the future who was connected to the future John Connor, whom Cameron interrogated, mimicked the appearance and personality of, and subsequently killed]].
* A positive example occurs on ''Series/TheTwilightZone1959''. In the episode "Nervous Man In A Four Dollar Room", a small-time thug (Joe Mantell) is ordered to kill someone for the first time in his life. His long buried conscience refuses to go along with committing murder and takes over as the dominant personality.
* In one episode of ''Series/TalesFromTheCrypt'' a lonely man's only companion is his own split personality. When the man starts dating a therapist, said split personality is afraid that she will destroy him and tries to goad the man into killing her. When the guy refuses, his other half decides to "kill" him and take over his life. In the end, the more assertive personality has cowed his former boss and is on the fast track to becoming an executive and is married to the therapist.
* This is extremely common on ''{{Series/Supernatural}}'', due to the prevalence of demonic possessions and sympathetic monsters who want to retain their humanity but are incapable of controlling their predatory instincts. Memorable non-possession examples include Lenore and [[spoiler: God-mode Castiel, after he ingests the Leviathan]]. Throw in manly tears, and you could [[OnceAnEpisode almost turn this into a drinking game]].
* ''Series/{{Warehouse 13}}'': "[[WhamEpisode The Ones You Love]]" reveals that [[spoiler: the "Brother Adrian" that Artie's been dealing with all season is a hallucinatory manifestation of an increasingly powerful EnemyWithin. Just as Artie realizes this, it grows powerful enough to assume control completely.]]
* ''Series/DoctorWho'': The Eleventh Doctor has to fend off the Cyber Planner that calls itself [[EvilIsHammy Mr. Clever]] when it attempts to take over his mind. Seeing Creator/MattSmith ActingForTwo in a Sméagol/Gollum type fight is equal parts awesome and hilarious, with a touch of bone-chilling sinister thrown in by the [[Creator/NeilGaiman the episode's author.]]
* In the live-action drama version of ''Series/DeathNote'', Mello starts off as a darker split personality of Near, kept ''mostly'' in check. Towards the end, [[ImHavingSoulPains Near collapses]], and Mello takes over, complete with EvilCostumeSwitch.
* In the "One Last Prayer" episode of Creator/{{HBO}}'s 80s anthology ''The Hitchhiker'', a pretty and talented singer called Miranda invents an image for herself guaranteed to succeed, but finds it starting to take over. [[spoiler: She fights back, but [[TheBadGuysWin The Bad Girl Wins]].]]
* In ''Series/TheFlash2014'', this happens to [[spoiler: Caitlin Snow]], who gets taken over by her [[spoiler: Killer Frost]] personality if she uses her powers.

* "[[https://www.youtube.com/watch?v=RvEOqqim9F0 My Name is Allen]]" by Music/StoneSour.
-->''There's only room in here for one / And I've decided it's not you\\
I had to do what must be done / You would have done it too''
* This happens to the protagonist of Music/NineInchNails's Music/TheDownwardSpiral over the course of the album.
-->''The me that you know, he doesn't come around much\\
[[ThatManIsDead That part of me isn't here anymore]]''
--->-- "The Becoming"

[[folder:Music Videos]]
* The video for Music/FooFighters' "Breakout" has a meek Dave Grohl becoming the rock star Dave Grohl after losing both his medication and [[HeroicBreakdown his shit]] (inspired by ''Me, Myself and Irene'', on which the song was included).

* ''Toys/{{Bionicle}}'': In one of the alternate universe Takanuva stumbles through, the alternate [[BigBad Makuta Teridax]] absorbs Matoro, who failed in his mission to save Mata Nui in this universe. When Makuta absorb other beings, they normally absorb their bodies and minds, but Matoro fights back, killing himself and Teridax, becoming the hero he was destined to be.

[[folder:Pro Wrestling]]
* Along with wrestling as himself, Wrestling/MickFoley also wrestled under the personas known as "The Three Faces of Foley", which consisting of [[TheBerserker Cactus Jack]], [[PsychopathicManchild Mankind]], and [[NewAgeRetroHippie Dude Love]]. No one ever knew when he switch personas, resulting in one hell of a WhamEpisode when he let Catcus Jack take over to fight Wrestling/TripleH in 2000.
* Black Serpent and Timothy Krane got to Bill Black in Fringe Pro Wrestling and manipulated him into suppressing his split personality Will White.[[/folder]]

[[folder:Tabletop Games]]
* The Harrowed from TabletopGame/{{Deadlands}} are constantly in danger of this, since they owe their very existence to the demons possessing them. Except [[TheDragon Stone]]. He's already such an evil, cruel, monstrous asshole that [[HorrifyingTheHorror his Manitou just hides in the back of his head and tries not to call attention to itself]].
* What happens to [[GoneHorriblyWrong Experiments]] in ''TabletopGame/BleakWorld'' if they get [[EvenEvilHasStandards too inhumane for the voices to stomach]] or are a little to [[PowerAtAPrice liberal with their magic]].

[[folder:Video Games]]
* In ''VideoGame/TwistedMetal: Head-On'', [[spoiler: Marcus Kane gives into Needles Kane, aka Sweet Tooth. Interestingly, however, it's not a complete takeover, but rather they seem to be working together, thereby making Dark Tooth and Tower Tooth (the two cars they drive together) the strongest in the game.]]
* The bad ending of ''VideoGame/SoulNomadAndTheWorldEaters'' involve this, with Gig using your greed to destroy the main character's soul and taking over his/her body. [[spoiler:The 'bad' ending of the Demon Path reverses the roles, with the main character destroying Gig instead.]]
* Both the good and the evil ending of ''TheSuffering: Ties That Bind'' [[spoiler: results in either Torque or Blackmore wiping the other personality out completely.]]
* The bad ending of ''[[{{Manhunt}} Manhunt 2]]''- achieved by killing people as gruesomely as you can - has [[spoiler: Leo killing off Daniel's personality and becoming the sole resident of his body]].
* Near the end of ''VideoGame/{{Planescape Torment}}'' you get trapped in a place where you encounter three of your previous "incarnations". One wants to take you over so and another simply wants to destroy you. If you manage to forcibly take over the other two or get them to merge with you, you will gain their memories (and a ton of XP). If you fail, you have to destroy them and their memories are lost forever. The third takes no convincing to get him to merge with you and is more than happy to.
* ''VideoGame/VampireTheMasqueradeBloodlines'' has a scene where, after being led along by the two, you finally confront [[spoiler: Jeanette and Therese Voermann -- wait, make that Tourette Voermann. One half of her face is done up in Therese's professional businesswoman style, while the other half is done up in Jeanette's slutty schoolgirl style, and the two sides speak in turns about wanting to kill the other]]. Depending on the dialogue you choose, either [[spoiler: Jeanette kills Therese, Therese kills Jeanette, or the two personalities decide to put aside their differences and coexist.]]
* Done very strangely in the ''VideoGame/{{Warcraft}}'' series; Arthas was a paladin who is corrupted by the Lich King, becomes his champion, then later merges with him, but then ''Arthas takes over the Lich King'', an entity of godlike mental power. A dark lord taken over by another dark lord [[spoiler: who is later revealed to be slightly less evil than everyone thought him to be]] when they became one dark lord.
* One of the main plot points of Riku's story in ''VideoGame/KingdomHeartsChainOfMemories'' and its remake is that Riku is fighting off the last of Ansem's darkness within his Heart. Several times he almost falls to it, and once he actually does, however how it happens depends on the version. In the original, after completely dominating Lexaeus in their fight, the latter ''blows himself up'' in an attempt to drag the latter down into the Darkness. However, in the nick of time, he is able to resist. In the remake, after a stalemate battle, Riku lunges at Lexaeus to finish him off, only to be backhanded into the ''ceiling'' and passing out. Unconscious Riku's body is possessed by Ansem who then kills Lexaeus in ''one hit'' before Mickey appears and frees Riku.
* ''VideoGame/InazumaEleven'': Fubuki Shiro, who is taken over by Atsuya, his inner mind's high ego little brother.
* A positive example can be found in ''VideoGame/DeadlyPremonition'', where [[spoiler:upon being traumatized and locked in the White Room by Forrest Kaysen, Francis Zach Morgan develops the personality of Francis York Morgan, who takes dominant control in order to protect Zach. At the endgame, Zach is given back control for the final confrontation with Kaysen.]]
* In ''VideoGame/MortalKombat9'' a positive example appears in Ermac's Arcade Ladder ending. [[spoiler:The soul of King Jerrod, Kitana's father and Sindel's husband,]] eventually becomes dominant in Ermac and becomes Edenia's protector again.
* ''VideoGame/SuperRobotWarsAlpha 3'': Subverted [[spoiler: When Cobray Gordon was formed from the fusion of Ayin and Ingram, Ingram tries to take over Ayin's body but ultimately realizes that he himself is being absorbed by Ayin]]
* In ''Franchise/TheElderScrolls'' series, Sheogorath, the [[OurGodsAreDifferent Daedric Prince]] of [[MadGod Madness]], is [[spoiler:a split personality of Jyggalag, the Daedric Prince of Order]]. When the other Daedric Princes grew afraid of how powerful [[spoiler:Jyggalag]] was becoming, they used their powers to [[HijackingCthulhu curse him into becoming the very thing he hated the most]]. Once every Era, [[spoiler:Jyggalag]] is allowed to retake control in an event known as the Greymarch. He destroy's Sheogorath's [[EldritchLocation realm]] (and formerly his own), the Shivering Isles. Once the destruction is complete, Sheogorath retakes control and must rebuild in a ViciousCycle. The events of the ''Shivering Isles'' expansion for ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'' end with you [[spoiler:[[LiteralSplitPersonalities splitting them into two separate and distinct beings]] by taking on the mantle of Sheogorath ''[[DeityOfHumanOrigin yourself]]'']].
* In ''VideoGame/FalloutNewVegas'', Lily's aggressive alternate personality, Leo, who usually appears to her as a completely separate entity standing beside her, will take over her body when she goes down to 1/4 of her HP, making her unresponsive to any command. Witnessing this triggers her companion quest where you discover that she's only been taking half-dosages of her meds. You can convince her to keep doing what she's doing, take the full dosage to suppress Leo completely at the cost of making her weaker in combat, or stop taking them altogether, which causes Leo to come out at 1/2 HP but makes her much stronger in combat. Similarly, Dog/God in ''Dead Money'' may have one of his personalities destroy the other, or merge the two.
* In ''VideoGame/CounterfeitMonkey'', this doesn't happen ''all'' the way but there are still FridgeHorror implications of it after Alex and Andra (who started out as separate people, but voluntarily fused together as one person to make escaping the authorities easier) are [[SadisticChoice forced to decide]] whether to betray Alex's father or Andra's boyfriend. Immediately after they make their decision, the personality who got the upper hand in the decision suffers a brief bout of dizziness and from then on becomes the semi-dominant personality. It's done subtly enough that the player might not notice until the very end of the game (when it's revealed that they no longer have equal control of their body and hence cannot be separated), but examining the PC at any point afterwards will reveal that either Alex or Andra feel as if their body has become more the other personality's than their own and that they're more of a hanger-on than a co-partner now, and there's also a subtle increase in pronoun usage for the dominant personality (a greater number of "I"s from Alex, or a greater number of "you"s from Andra).
* Averted in ''VideoGame/AmericanMcGeesAlice''. Alice's BattleInTheCenterOfTheMind with The Red Queen would have determined which of her personalities would be dominant and which would be cast down and forgotten.
* In ''Mystery Trackers: The Void'' Marius Void's criminally-inclined "brother" Sirius takes over his body after killing his psychiatrist, who'd been supplying drugs to suppress the transformation.
* Threatened by Krieg's "good" voice in ''VideoGame/Borderlands2'', which has told the dominant personality that if Krieg ever kills an innocent, he will seize control and commit suicide.

[[folder:Visual Novels]]
* This is the major twist in the freeware VisualNovel ''VisualNovel/OriOchiOnoe''. [[spoiler:The protagonist used to be in love with the sweet and gentle Ori, but Ori turned out to be a split personality of the more violent and temperamental Ochi with the two personalities referring to each other as "sisters" and leading separate lives. Unfortunately, a later eye operation destroyed the Ori personality and left just the Ochi personality who the protagonist subsequently entered a very complicated and twisted relationship with. One of the game's endings has Ori regain control after the protagonist makes it clear that he loves only her, and another ending has the two personalities merge to create a more complete Ochi.]]
* ''VisualNovel/UminekoWhenTheyCry'': The main villain of the third arc is [[spoiler:Eva, who has a sort of ImaginaryFriend and LiteralSplitPersonality that looks like she did as a child. When Eva finds the gold, her SplitPersonality becomes Eva-Beatrice, and it's nicely proven that WithGreatPowerComesGreatInsanity. Over the rest of the arc, Eva's "human side" breaks down more and more, and she spends a lot of it locked in her room with a fever. But after [[MoralityPet George and Hideyoshi]] are killed, she snaps into outright AxCrazy-ness, starts using Evatrice's CatchPhrase, and shoots Battler.]]
* In ''VisualNovel/CinderellaPhenomenon'', [[spoiler:Varg was created by Mythos as a darker split personality of Lucette's knight Fritz that would gradually take over Fritz. Varg can initially come out only at night and can be banished by Lucette uttering the trust word Fritz told her, but later on he can come out during the day and Lucette can no longer easily call Fritz back. Fortunately for Fritz, however, his feelings for Lucette rubbed off on Varg and Varg ultimately erases himself so that Lucette can have Fritz back... provided you made the right choices for Fritz's good ending, that is]].

[[folder:Web Original]]
* A curious example in ''[[Machinima/RedVsBlueTheRecollection Red vs. Blue: Reconstruction]]'' - when an [=AI=] is implanted in a character, the effect is described as being "of the same mind", where the two entities share thoughts. Though the host is usually able to maintain his or her identity (even if free will is lost), Agent Maine (better known as [[TheJuggernaut the Meta]]) degenerated into a mindless husk after playing host to 7 different [=AI=]s ''at once'' and stayed that way even when the [=AI=]s were removed. Of particular note is the fact that all 7 [=AI=]s were [[LiteralSplitPersonality Literal Split Personalities]] of another [=AI=], the Alpha.
* ''Literature/WhateleyUniverse'': Sara Waite is really a [[CosmicHorror Great Old One]] who is supposed to evolve into The Kellith, a being who will wipe the earth of humanity and re-populate it with her spawn. She ends up having a fight to the death with The Kellith in a JourneyToTheCenterOfTheMind.
* Done in a masterfully nightmarish way in ''WebVideo/MarbleHornets''. In Entry #61, we're treated to a video of the hooded masked man stealing Tim's medication while Tim is in the bathroom during a coughing fit. After Hoody hides, Tim stumbles into the room and undergoes a disturbingly realistic seizure, then jerkily climbs to his feet and absconds, all with the heavy implication that his ''other'' personality, the original masked man, is back in the driver's seat. Amongst the evidence that Masky is in control is his pronounced limp- after his leg was previously broken, he'd been limping up to his last chronological appearance in the series.
* ''Webcomic/{{Homestuck}}'': [[spoiler:Calliope, a sweet and genuinely kind girl, shares a body with Caliborn, a barely restrained sociopath. At the end of Act 6 Act 3, Caliborn becomes not so restrained, escapes from his confines, and starts a session on his own, taking over their body completely and burying Calliope in the process. However, some characters believe that she may not be entirely dead and that in fact finding her might be the key to defeating Lord English once and for all. The author mocks Caliborn for doing this, since he stunted his own CharacterDevelopment by averting the SplitPersonalityMerge that Cherubs normally go through.]]
* ''Literature/{{Twig}}'': Late in the story Sylvester completely shuts down emotionally, entering into a HeroicSafeMode where his hallucinations of the friends he's left behind take control. This eventually culminates in the Evette persona, a manifestation of his pain and need to lash out, taking full control. She sets Sy on a self-destructive course between rebels and the local nobility, intending on a quadruple cross but in the end desiring to hurt as many people as possible before they finally go down, and Sy's friends are barely able to rescue him.
* In ''WebAnimation/FiftyPercentOff'', Haru has a whole collective of Harus inside his head who talk, argue, or play chess ("Haru, this is checkers") with each other. In Episode 8 the Impulsive Haru somehow shoots another Haru and takes direct control of the brain so he can go swimming, with the consequence that he shot the only Haru who knows how to read. [[spoiler:[[BrickJoke Then in Episode 18,]] the Haru Who Can Read [[HesBack makes his triumphant return to get Haru back on track after a loss.]] [[ComedicSociopathy The first step of which involves slaughtering a bunch of other Harus and building statues to himself in Haru's mind.]]]]

[[folder:Western Animation]]
* Norman Osborn undergoes this in ''WesternAnimation/SpiderManTheAnimatedSeries''.
-->'''Green Goblin:''' (to Harry Osborn) [[ThatManIsDead Your whining simp of a father doesn't exist anymore]]. I am the ultimate evolution of Norman Osborn!
* ''WesternAnimation/XMenEvolution'', episode ''Sins of the Son''. Charles Xavier discovers he has a son in Scotland, David Haller, and goes to meet him, only for two other boys to enter the fray as well. These three boys (David, Ian, and the evil Lucas) are all parts of the same being. Xavier tries to help expunge Lucas, [[spoiler: but ends up locking away David, forever losing his son as Lucas goes off, never to be seen again (as the series was cancelled before this story could continue).]]
* In ''WesternAnimation/SouthPark'', at the end of "City Sushi", the police allow [[spoiler:Dr. Janus]] to keep on thinking he's [[spoiler:Lu Kim]], since [[spoiler:Lu Kim owns the only Asian restaurant in town after City Sushi was destroyed]].
* In ''[[WesternAnimation/TotalDrama Total Drama All-Stars]]'' Mike was in the previous season was established as having several different personalities. [[spoiler: In the episode "Evil Dread" the previously unknown personality [[TheSociopath Mal]] is set free when Mike is hit in the head with a shovel, albiet slightly, as he switches in and out at random. Some episodes later Mike attempts to seal him away again by hitting his head on a large rock, [[NiceJobBreakingItHero but it only serves to imprison Mike in his own mind and give Mal free reign]].]]
* In the ''WesternAnimation/Ben10Omniverse'' episode "Max's Monster", [[spoiler:Max's EvilFormerFriend Phil]] [[TheBusCameBack comes back]] after a long stint in the Negative Zone mutated and insane after he was used as a test subject [[spoiler:for the Nemetrix]]. He frequently transforms into a savage energy eating monster with a mind of its own and begs the heroes to help him. Ben is suspicious but Max and Rook are willing to try. [[spoiler:Ben is ProperlyParanoid, since "Phil" soon admits that "there hasn't been a Phil in this body for ''years''". [[HydePlaysJekyll The monster personality has been in control the entire time]], and [[DeadAllAlong Phil is long gone]].]]
* In ''WesternAnimation/TheAmazingWorldOfGumball'' episode "The Name", when Gumball's discovery of his first name being Zach results in "Zach" becoming his own person, the latter tries to [[WrittenByTheWinners alter the former's memories]] to erase him from existence.
* ''WesternAnimation/AdventureTime'' has this happen to Simon Petrikov, as documented by [[ApocalypticLog his tapes.]] Although the moment in which he fully became the Ice King has yet to be shown onscreen, the tapes show him increasingly [[SanitySlippage slipping in and out of]] his [[SuperpoweredEvilSide current persona's]] mannerisms; while the later episode "Simon and Marcy" shows him initially ''resisting'' this, but the end of the episode makes it clear that [[LossOfIdentity he's losing himself]] and that [[DownerEnding this trope will soon occur]].
* ''WesternAnimation/TheAvengersEarthsMightiestHeroes'' has a rare consensual example -- Bruce Banner lets [[ComicBook/IncredibleHulk the Hulk]] take over his body as long as the Hulk works alongside the Avengers as a hero. Eventually, Bruce is allowed to have control for one day a month.
* ''WesternAnimation/{{Kaeloo}}'': The episode "Let's Play Grown-Ups" suggested that later in Kaeloo's life, her [[JekyllAndHyde alternate form, Bad Kaeloo]], would take over.

[[folder:Real Life]]
* An episode of the dramatized court-case anthology series ''The Judge'' dealt with a female [[SplitPersonality dissociative identity disorder]] patient who, in the episode's surprise twist, turned out to be the victim of her psychiatrist, who was having an affair with her FemmeFatale persona and plotting to destroy her original personality so the two of them could be together. While the script might've involved some dramatic exaggeration, there are real-life cases of secondary personalities in DID cases plotting to kill their primary selves, without recognizing that if they're successful, they'll die too.