So your story was a smash success, and you've gotten enough interest or capital to do a sequel. However, you fear that you fully explored all of the characters in the first story and of course it would stale your writing ability to [[SequelReset retread the same characters and events from the first story]]. So you need a way to not only stretch your storytelling chops, but also hand out enough {{Shocking Swerve}}s to keep the audience surprised. How do you do this?

Why, by turning one of the main [[FaceHeelTurn good guys into a bad guy!]]

[[TropesAreNotBad When done correctly]], a FaceHeelTurn can be shocking, compelling and tragic. Few things tug at the heartstrings like when [[BreakTheCutie a cutie is broken]] or when TheParagon crosses the DespairEventHorizon and [[GoMadFromTheRevelation goes bonkers over the unfairness of it all]]. [[TropesAreNotGood When done poorly]], the turn comes out of [[ShockingSwerve absolutely nowhere]] or [[CharacterDerailment betrays the expectations that had been set by the character's portrayal up til then]]. Audiences tend to become attached to their heroes and some become more "icons" than characters, leading to the audience feeling betrayed by not only that character, but the writers themselves.

If this is a prequel, and an enemy from the original is part of the group, then this is DoomedByCanon to happen.

A subtrope of FaceHeelTurn. Separate from (but not mutually exclusive to) SuddenSequelDeathSyndrome.

SuperTrope of RogueProtagonist, FallenHero, and TheParagonAlwaysRebels. See also RonTheDeathEater for fanfiction, and AdaptationalVillainy. Contrast ProtagonistJourneyToVillain, which is all about showing their slide to villainy onscreen.

'''WARNING: Contains ''major'' spoilers.'''



[[folder: Anime/Manga ]]

* Joker, the head of the British Library special forces in ''Anime/ReadOrDie''. Between the OVA, where he's on the side of the good guys, and R.O.D The TV, the death of Gentleman (the ManBehindTheMan of hundreds of years of British history who envisioned a sort of Utopia under the British Empire) shifts Joker into WellIntentionedExtremist territory, working toward what he sees as Gentleman's dream by means ranging from ethically dubious to outright evil.
* ''Anime/YuGiOh'' Season 4 turned Mai Kujaku, the gang's CoolBigSis, into an angst-ridden member of a villainous biker gang. It turns out she was tricked into HeelFaceBrainwashing by the arc's BigBad, Dartz.
* In the sequel to ''Manga/BoboboboBobobo'', Gasser switches sides and becomes a hair hunter to protect his [[RememberTheNewGuy previously]] unmentioned sister from harm.
* In the third season of ''Anime/CardfightVanguard'', Kai (the resident InvincibleHero) is on the receiving end of a HannibalLecture and ends up BrainwashedAndCrazy, becoming the emissary for the main bad guys.
* Season 3 of ''LightNovel/ShakuganNoShana'' [[spoiler: has the male protagonist, Yuji Sakai, of the first two seasons, suddenly becoming the BigBad, leaving the female lead and love interest Shana shocked and confused.]]
* Played straight and zigzagged in ''Manga/TokyoGhoul''[=:Re=], which takes place after a two year TimeSkip:
** [[TheCutie Hinami]] Fueguchi was [[CorruptTheCutie enticed]] to join [[TheSyndicate Aogiri Tree]], through her desire to become stronger. She returns as a prominent member handling the group's intelligence network.
** PluckyComicRelief Seidou Takizawa turns out to be NotQuiteDead, and returns as an AxCrazy [[HalfHumanHybrid One-Eyed Ghoul]] serving as Aogiri's first successful SuperSoldier. He proceeds to slaughter his way through every Investigator he crosses paths with, taking the time to chat with a former pupil before tearing her head off because she used to talk during lectures.
** Played with, depending on [[GreyAndGrayMorality which side]] has the SympatheticPOV. Ken Kaneki returns as AmnesiacHero Haise Sasaki, working for the [[HunterOfMonsters CCG]] as a Ghoul Investigator and mentor to an experimental squad of SuperSoldiers. While he remains the protagonist, his former friends now have to worry about him hunting them down if they cross paths again.
* Happens to [[spoiler:Gennai]] in ''Anime/DigimonAdventureTri'', who was originally TheMentor for the kids. Here, he's one of the bad guys. [[spoiler: Or so we thought. The Man in Black is actually a shapeshifting creature created by Yggdrasil for its own evil plans and stole Gennai's form.]]

[[folder: Comics ]]

* Jean Loring in ''ComicBook/IdentityCrisis'', who went completely off her rocker to try winning back the affection of her ex-husband, [[ComicBook/TheAtom Ray Palmer]].
* The survivors of ''ComicBook/CrisisOnInfiniteEarths'' (Superboy-Prime, Superman (Kal-L), and Alexander Luthor) all became contemptuous of UsefulNotes/{{the Modern Age|of Comic Books}} Franchise/DCUniverse and launched a scheme that would forcefully return things to UsefulNotes/{{the Silver Age|of Comic Books}} status quo, whether the universe was ready or not, on ''ComicBook/InfiniteCrisis''. Though it should be noted that [[spoiler:Kal-L was just an UnwittingPawn, he turned back to Face the second he realized what was really going on, and ultimately [[HeroicSacrifice gives his life bringing down Prime]]]].
* ComicBook/{{Supergirl}}: Post-Crisis Linda Danvers retired from superheroics after ''Comicbook/ManyHappyReturns'', but returned in ''ComicBook/{{Shadowpact}}'', transformed into a vengeful "Fallen Angel".
* ComicBook/{{Batgirl 2000}}: Cassandra Cain during DC's ''OneYearLater'' storyarc. This was not a popular storyline (she was quite OutOfCharacter even ''aside'' from the evil) and eventually got {{Ret Con}}ned into mind control.
* Max Lord had always been depicted as a somewhat egotistical businessman who recreated the Justice League in part to make himself look good but ultimately proved to be a fairly honorable person. Then came ''ComicBook/InfiniteCrisis'', in which he turns out he founded the new League in order to undermine all superheroes. And even worse, it reveals that he was ''always'' evil, despite readers having seen his inner thoughts at multiple points in that Justice League run to prove otherwise.
* In ComicBook/WorldWarHulk we learn that Miek, who was a friend and ally of Hulk in ''ComicBook/PlanetHulk'', was the one who let the explosion destroy Sakaar just so he would reach [[UnstoppableRage the WorldBreaker stage.]] This at least was foreshadowed by him passing a DespairEventHorizon at the apparent extinction of his species, leaving him the only one of the Warbound without a happy ending.
* In [[ComicBook/TheUltimates The Ultimates 2]], Black Widow is revealed to be [[TheMole a mole]] working for the Liberators and her native country, Russia.


[[folder: Fan Fiction ]]

* Inverted in ''Fanfic/ThePrayerWarriors'', [[Literature/PercyJacksonAndTheOlympians Clarisse, Annabeth and Grover]] were villains in ''The Evil Gods Part 1'', but they inexplicably get brought back as being on the Prayer Warriors' side (in addition to being brought BackFromTheDead, but [[DeathIsCheap that's another issue]]). Then again, this might be a straight example when you consider that the Prayer Warriors murder anyone who disagrees with them.
** Played straight with Hagrid. He's introduced in "Battle With The Witches" as a "secret Christian" inside Hogwarts, and helps the Prayer Warriors. He continues to do so in "Titans Strike Back," but when Draco meets with him while planning on infiltrating the rebuilt Hogwarts, Hagrid springs a track on him and reveals that he was EvilAllAlong.
* In ''Fanfic/HalfLifeFullLifeConsequences'', Gordon Freeman, TheHero from canon and the protagonist's heroic brother in this fanfic, comes BackFromTheDead in "What Has to Be Done", as a "zombie goast" who wants to kill his brother out of revenge, [[spoiler:and again as a BrainwashedAndCrazy slave of the Combines in "Free Man", although once he's defeated, he [[DyingAsYourself dies as himself]].]]


[[folder: Film ]]

* In the original ''Film/RoboCop1987'', the CEO of Omni Consumer Products is merely an amoral old man who really doesn't do anything outright villainous, but shows little empathy for others. In [[Film/RoboCop2 the sequel]], he's a flat-out CorruptCorporateExecutive.
* ''Film/TronLegacy'' does this to [[spoiler:Tron himself aka Rinzler, courtesy of being [[BrainwashedandCrazy corrupted and reprogrammed]] by [[BigBad Clu]]. He has a HeelFaceTurn and a HeroicSacrifice near the end of the film, though.]]
** For that matter, Clu himself.
* ''Film/{{Star Trek VI|The Undiscovered Country}}'' turns Admiral Cartwight from ''Film/{{Star Trek IV|The Voyage Home}}'' into a co-conspirator with the bad guys.
** And the film was going to have Saavik as another conspirator, until Gene Roddenberry personally stepped in and forced them to change her to a new character, Valeris; he recognized that turning a beloved character into a murderous traitor wouldn't sit well with fans. Imagining her as Saavik makes Spock's stunned reaction to her betrayal make a bit more sense.
* The first ''Film/MissionImpossible'' film turns Jim Phelps, the unwavering mastermind of the original series, into a bitter cynic who betrays his team for a multi-million dollar payoff. To say that fans of [[Series/MissionImpossible the original series]] were angry would be an understatement. Greg Morris, who played Barney Collier in the original, walked out of the movie in disgust, while Peter Graves and Martin Landau also voiced their displeasure (Graves turned down an offer to reprise his role as Phelps because of this).
* Ugg the alien bounty hunter who was one of the heroes in the first three ''Film/{{Critters}}'' film is the main villain in the fourth film.
* Inverted in ''Film/Terminator2JudgmentDay''. The robot played by Arnold Schwarzenegger was the antagonist in the first film. In the sequel Arnold is the one protecting John Connor this time, while the robot played by Robert Patrick is the villain. At the time this was the big twist, but [[ItWasHisSled it's now widely known]].
* ''Film/CaptainAmericaTheWinterSoldier'' reveals that the eponymous Winter Soldier is Cap's old war buddy Bucky Barnes, now BrainwashedAndCrazy. Luckily, he's redeemed at the end.
** It also does this to many [=SHIELD=] agents who had appeared throughout the [=MCU=]'s existence who were revealed to be [[spoiler:Hydra moles]], including Jasper Sitwell and Senator Stern.
* Although neither side was ever shown to be completely in the right or wrong (being a Captain America movie, we can assume that Team Cap were the "heroes" and Team Iron Man the "villains"), the two sides of ''Film/CaptainAmericaCivilWar'' rapidly approach lethal measures in the airport fight, culminating in a shot meant for Falcon from Vision's Mind Stone instead hitting War Machine's Arc Reactor, cutting off the suit's power and paralyzing him from the waist down in the resulting crash. Despite this, Iron Man still relents upon finding Cap and Bucky in Siberia, until Zemo reveals that the Winter Soldier killed Stark's parents, launching Iron Man into a rage-fueled, NoHoldsBarredBeatdown on the pair.
* Most of the Hulk's first scene in ''Film/ThorRagnarok'' is spent beating the ever-loving snot out of Thor. Even when Thor survives the fight, Hulk is more antagonistic towards Thor than previous films might have suggested. It takes Black Widow's message from the end of ''Film/AvengersAgeOfUltron'' to snap Hulk out of it and return him to Bruce Banner.
** Also inverted in the same film. Loki, who was the villain of ''Film/{{Thor}}'' and ''Film/TheAvengers2012'', becomes a reluctant ally with his own reasons for doing so in ''Film/ThorTheDarkWorld'', but is fully redeemed by the end of ''Ragnarok''.
* Koba in ''Film/RiseOfThePlanetOfTheApes'' wasn't the nicest ape, but he still had justification for the things he did and supported Caesar. In ''Film/DawnOfThePlanetOfTheApes'', he becomes the BigBad as his hatred of the humans becomes so great that [[FalseFlagOperation he attempts to assassinate Caesar and sets fire to their camp and blames the humans to start a war against them]].
* ''Film/JurassicWorld'', Henry Wu is a MorallyAmbiguousDoctorate who strikes a deal with the BigBad to explore the possibility of weaponizing dinosaurs. He [[spoiler: deliberately engineers the I. Rex to be strong and smart enough that it will inevitably escape, even though this would endanger everyone on the island (implied to be thousands of people when it happens) and destroy any future the park might have had as a business]]. Harboring no loyalty towards Masrani (his boss) or the dream of the late John Hammond, his sole motivation in the film seems to be ForScience. This is rather jarring when compared to his appearance in the first movie, where he never showed any antagonism towards the other characters or malevolent intent in creating dinosaurs (though admittedly, he was a pretty minor character).
* ''Film/PacificRimUprising'' has [[spoiler: Newt become the BigBad after his repeated drifting with a Kaiju Brain allows the Precursors to [[BrainwashedAndCrazy get inside his head]].]]


[[folder: Literature ]]

* In the first story of G.K. Chesterton's ''Literature/FatherBrown'' series, detective Aristide Valentin of the Paris police force is a likable InspectorLestrade to the title character, totally fooled by Father Brown's ObfuscatingStupidity but competent enough to follow the trail of clues the little priest leaves for him. In the next story, [[CharacterDerailment however]], he becomes a StrawAtheist who murders a man to prevent him from leaving money to the church in his will. (And, for extra irony points, the villain from the first story is subsequently given a HeelFaithTurn to become TheWatson.)
* In ''Literature/InheritanceCycle,'' [[EnsembleDarkhorse Murtagh]] turns evil in the second book, because [[BigBad Galbatorix]] [[IKnowYourTrueName knows his true name]].
* In ''Literature/DoraWilkSeries'', after being Dora's staunch ally for first five books, Katarzyna turns against her in the sixth one, suddenly having issues with Dora's mixed blood - a fact known even before the series started. She mostly has problems with the fact that by the series finale, Dora doesn't even try to hide her mixed heritage, which Katarzyna finds disgusting.
* Atticus Finch, an iconic hero in ''Literature/ToKillAMockingbird'', becomes a senile old racist in its sequel, ''Literature/GoSetAWatchman'' (written first but published and set afterwards). This is shocking both in and out of universe, with Atticus's daughter expressing her distaste, and many critics have also voiced displeasure at the dismantling of one of the most inspiring heroes in American history.
* ''Literature/HarryPotterAndTheOrderOfThePhoenix'' has Harry returning to the Weasley family only to find out that [[TheComicallySerious Percy]] has fallen out with everyone and [[MyCountryRightOrWrong sided with the Ministry of Magic]] ahead of the upcoming war.
** Similarly, ''Theater/HarryPotterAndTheCursedChild'' reveals that [[InspirationalMartyr Cedric]], a LovableJock who put HonorBeforeReason in both Quidditch and the Triwizard Tournament, would have become a [[ANaziByAnyOtherName Death Eater]] had he lost the latter. This is one major reason that [[FanonDiscontinuity some fans won't consider it canon]].


[[folder: Live-Action TV ]]

* Sikozu in ''Series/{{Farscape}}: The Peacekeeper Wars.''
* In ''Film/KamenRiderXSuperSentaiSuperheroTaisen'', former [[Series/KaizokuSentaiGokaiger Gokai Red]] Marvelous actually takes command of a LegionOfDoom to further his quest for the Greatest Treasure. [[spoiler: All a plan between the Super Sentai and the Kamen Riders to manipulate the bad guys, of course]].
** ''All'' the Gokaigers in the usual teamup with Go-Busters. Naturally, they were also faking it.
* During the original run of ''Series/DoctorWho'', Chancellor Borusa had in the past been depicted as a politically motivated member of the Time Lords High Council, but ultimately someone whom the Doctor could work with and even regard as a friend. In "The Five Doctors", he turned out to be the villain, orchestrating a mad scheme to resurrect Rassilon and gain immortality.
** Admittedly, every time the show returned to Gallifrey, it seemed that more of the cracks in the Time Lords' "perfect society" would show, to the point where the Doctor would call them out, declaring them, "the oldest civilization, decadent, degenerate and rotten to the core!" By the time of the new series, the entire Time Lords species had crossed a collective MoralEventHorizon, plotting to destroy all of time to preserve themselves. This ended up being retconned, however, as the actions of a small minority of Time Lords, after which they save the Doctor's life by granting him a new regeneration cycle.
* In an episode of ''Series/BurnNotice'', TheWoobie hires Michael to rescue his kidnapped daughter. In the next episode, the same man is the villain, as his RoaringRampageOfRevenge against the men responsible claims innocent lives and Michael takes it upon himself to stop him.
* ''{{Series/Charmed}}'':
** Cole Turner began as a straight up AntiVillain before undergoing a HeelFaceTurn. He was possessed by an evil entity in Season 4 and [[spoiler: forced to be killed]]. When he returns in Season 5 he's presented as a straight-up villain.
** The Crone was a TrueNeutral in her first Season 5 appearance - calling a truce between good and evil to prevent bloodshed over Wyatt Halliwell. Her second appearance has her as a villain who tries to kidnap the child herself.
* ''Series/RoboCopPrimeDirectives'' sees Alex Murphy's son, Jimmy, as an executive of OCP--[[SmugSnake a typical]] [[CorruptCorporateExecutive OCP executive]] as a result of the death of his father (and unknown to him until later, becoming [=RoboCop=] and later his mother. [[spoiler:That said, he does pull a HeelFaceTurn at the end of part 3.]]

[[folder: Professional Wrestling ]]

* This often happens to some wrestlers who are lower down on the card, especially in developmental. While creative works out the kinks in their character, they may just randomly appear in a different role on a new episode. For example they might be a face in their first few appearances and then inexplicably switch to heel.


[[folder: Radio ]]

* Nicholas Adamsworth (voiced by Dick Beals), a minor character from ''Radio/AdventuresInOdyssey'', was an ethical, well-meaning child-prodigy in his first two appearances. He came back many episodes later as a hacker who changed people's grades to bribe some students and to get revenge on others. His change in character is lampshaded, but the reasons for it are never actually explored beyond a nonchalant handwave on how some people change for the worse over time.


[[folder: Videogames ]]

* [[{{UsefulNotes/Masamune}} The Masamune sword]] in ''VideoGame/ChronoCross''. In the ''VideoGame/ChronoTrigger'', the Masamune is a coveted magical weapon which is said to be the only the only weapon capable of hurting the wicked sorceror, Magus. It's outright said many times that only the [[TheChosenOne Legendary Hero]] can wield the sword and at one point, said Hero even goes through a SecretTestOfCharacter which allows the sword to recognize him as its true owner and unlock its full potential. Then, in the sequel, the Masamune is explicitly stated to be an "evil" sword and anyone who wields it will immediately go insane. However, this is {{Hand Wave}}d in that the Masamune is sentient and inhabited by two mischievous young spirits. When their big sister shows up and smacks some sense into them, the Masamune becomes good again.
* Gray Fox, Schneider and Dr. Pettrovich were originally on Solid Snake's side in the first ''VideoGame/MetalGear''. In ''VideoGame/MetalGear2SolidSnake'', all three defected to Zanzibarland for personal reasons.
** ''VideoGame/MetalGearSolid2SonsOfLiberty'' cheerfully subverts this - the villain claims to be Solid Snake, but he clearly isn't.
** Sigint, Para-Medic and Zero in ''VideoGame/MetalGearSolid4''. It can be argued that their creation in the first place was to explain the StartOfDarkness which lead to the creation of "The Patriots", but few can argue that it's a shock to learn that the [[MorallyAmbiguousDoctorate amoral "Dr. Clark"]] we heard about in the first game was the sweet and flighty Para-Medic (it doesn't help matters that the first game retroactively misgendered Dr. Clark as a male).
* In the 2009 VideoGame/BionicCommando game the BigBad is revealed to be [[spoiler:Super Joe, the war hero you rescued in the original Bionic Commando.]]
* ''VideoGame/FinalFantasyX2'' inverts it. Tromell Guado was TheDragon to Seymour, actively sending people out to kill the protagonists after discovering they murdered Seymour, along with destroying the evidence that Seymour killed his own father. In the two year TimeSkip the entire Guado race suffered a collective MyGodWhatHaveIDone - and were exiled to the Macalania Woods. One sidequest is preventing the Ronso from slaughtering the tribe. If the player does things correctly [[spoiler: Tromell will become the new leader of the Guado and direct them towards a brighter future]].
* ''VideoGame/DiabloII'': The protagonist of the original is now the Big Bad.
** Justified in that at the end of the first game the protagonist [[spoiler: was forced to take Diablo's soul into his own body in order to contain him. The simple explanation was that it didn't work.]]
** The other heroes, the Mage and the Rogue, also become bosses. It ''is'' a CrapsackWorld after all.
* Lloyd Irving in ''VideoGame/TalesOfSymphoniaDawnOfTheNewWorld''. Well, sort of. [[spoiler: It was an impostor and the real Lloyd was only hindering your goals because he was trying to set things right as well.]]
* In the ''VideoGame/WingCommander'' video game series, the game Wing Commander III: Heart of the Tiger had [[spoiler:Col. Ralgha nar "Hobbes" Hhallas who was throughout game ''2'' a ProudWarriorRaceGuy who was disgusted with his race's lack of honor suddenly do a FaceHeelTurn in which he turns out to have been a sleeper agent hiding behind a fabricated personality]].
** Likewise, the BigBad of ''Wing Commander IV: The Price of Freedom'' [[spoiler: turns out to be Admiral Tolwyn, who lost his direction in life and ultimately went rather nuts once he no longer had a war to fight. Although he was something of a jerk towards your maverick ace character throughout the series, he was also mostly the main BigGood.]]
* This happens to heroine turned ActionMom, Sophitia Alexandra, in ''VideoGame/SoulCalibur IV''; where she's made to defend VideoGame/SoulEdge in order to save her daughter's life.
** It also happens to the eponymous Soul Calibur itself in the fourth game; when the sword reaches full power and gains sentience, it's revealed that the Calibur, long thought to be the "good" sword throughout the series, is technically just as "evil" as the Soul Edge. The difference is that the Soul Edge likes to spread chaos and misery while the Soul Calibur [[WorldOfSilence wants tranquility, order and peace... by freezing the entire world solid]].
* Vladimir Lem in ''VideoGame/MaxPayne2TheFallOfMaxPayne''. It wasn't that he was a particularly nice guy to begin with, being a high-ranking member of the local Russian mob as well as [[MadBomber more fond of explosives than is strictly healthy]], but he was a WorthyOpponent in an EnemyMine situation. As Max himself puts it:
--> ''"Vladimir was one of those old-time bad guys with honor and morals, which made him almost one of the good guys. None of us was a saint."''
* ''{{VideoGame/Contra}}: Shattered Soldier'' reveals that the Blood Falcon Commander is none other than Lance Bean, Bill Rizer's partner from earlier games. [[WellIntentionedExtremist He went insane]] trying to reveal the GovernmentConspiracy he and Bill were duped into helping cover up. Likewise, in ''Neo Contra'', [[spoiler: Lucia, player 2 in ''Shattered Soldier'']] is revealed to be part of the QuirkyMiniBossSquad and dies attempting to kill Bill and exterminate humanity for reasons which are not even vaguely explained.
* Alex Mercer becomes the BigBad in ''VideoGame/{{Prototype 2}}'' after crossing the DespairEventHorizon. The fandom has been [[BrokenBase split]] over this.
* ''VideoGame/WorldOfWarcraft'' has gone ''hard'' on various characters from the [[VideoGame/{{Warcraft}} previous games]] or the [[Franchise/WarcraftExpandedUniverse expanded universe]] in order to turn them into bosses which may be killed for loot. "Going mad," is apparently an occupational hazard for lore characters, as it's the most common excuse used to turn them into raid bosses. This list includes Illidan Stormrage, Kael'Thas Sunstrider, Malygos, Norzdormu, Fandral Staghelm, and Archbishop Benedictus.
** Illidan is a notorious example, to the point where Blizzard has vowed to one day bring him back and redeem him to make up for it. They even admitted that they only made him a villain so the expansion would have a popular character to confront and get loot from. In ''VideoGame/WarcraftIII'' Illidan was a complex AntiHero who used any means necessary to save his people, but despite fears from those around him never succumbed to the corruption of the dark powers he was toying with. Come the Burning Crusade expansion, he's been "driven mad" and turned to evil with no adequately satisfying explanation.
** Blizzard also expressed regret over Kael'thas's characterization, but after almost immediately bringing him back from the dead as an even more desperate Legion pawn, figured they missed their chance to properly repair his character.
** Malygos the Spell-weaver was introduced in the books as the Aspect of the Blue Dragonflight and protector of all magic in Azeroth, a friendly and wise dragon, who was only brought down when Deathwing wiped out most of the blues 10,000 years ago. Malygos then participated in the defeat of Deathwing in modern times, and the blues are shown as slowly coming back from the brink. Then he inexplicably decides to wipe out all mortal magic-users and becomes a bad guy, forcing Alextrasza the Life-binder to help put him down.
** The Zandalari trolls were introduced as allies of Horde an Alliance alike, seeking to stop the return of Hakkar and record the history of the collapsing Drakkari troll empire. In ''Cataclysm'' they began inciting the Amani and Gurubashi to reclaim their empires due to growing fears about trolls being wiped out. ''Mists of Pandaria'' escalated this when the Zandalari willingly joined forces with [[LawfulEvil the Thunder King]]. Here their reason is finally explained: [[DrivenToVillainy The Cataclysm is causing their homeland to sink into the ocean; without a new homeland they'll be wiped out]].
* The AxCrazy BigBad of ''VideoGame/ArmyOfTwo 3: The Devil's Cartel'' is revealed to be [[spoiler: Salem, one of the two main characters from the first two games.]]
* In ''VideoGame/FireEmblemAkaneia'', Hardin is on the hero's side in Shadow Dragon. In Mystery of the Emblem's second book, it is revealed that he has turned evil. [[spoiler:This is due to the BigBad of the first game corrupted Hardin with an ArtifactOfDoom, which exploited Hardin's insecurities due to not having the love of Nyna, who was only politically married to him.]]
* [[spoiler:Penelope Mouse]] from ''Franchise/SlyCooper'' turns bum at some point between [[VideoGame/Sly3HonorAmongThieves the third]] and [[VideoGame/SlyCooperThievesInTime fourth]] game, [[AssPull and it came right the hell out of nowhere]].
* ''[[VideoGame/DonkeyKong Donkey Kong Jr.]]'', the only professional game in existence to treat [[Franchise/SuperMarioBros Mario]] as the main antagonist.
** Inverted with [[VideoGame/YoshisIsland Raphael the Raven]], who debuted as a boss, only to suddenly be one of Yoshi's friends in ''VideoGame/TetrisAttack'' and an ally in ''VideoGame/PaperMario64''.
* Leon Silverburg in the ''VideoGame/{{Suikoden}}'' series went from a [[VideoGame/SuikodenI recruitable ally]] to a WellIntentionedExtremist in [[VideoGame/SuikodenII the sequel]]. This is a justified example, though - the stories are always set in different countries (and different points in time, though ''II'' is only several years after ''I''), and so the characters who do reappear will take different approaches based on who they're working for. Leon isn't even a villain anyway, he's just taking a different approach (''Suikoden'' thrives on GreyAndGrayMorality), so he's not really that different from the original game in terms of personality.
* ''Videogame/{{Dead Rising 3}}'' brings back [[spoiler:Isabella Keyes]] as the BiggerBad and WellIntentionedExtremist behind all of the events of that game. In a lesser example, [[spoiler:Chuck Greene]] becomes a crime boss [[spoiler:to provide his daughter Katey with more Zombrex. This drove away his LoveInterest Stacey from the previous game and Katey, who took on a different name "Annie" and ran away from home.]]
** Also, in the AlternateContinuity of ''Dead Rising 2: Off the Record'', [[spoiler: Chuck Greene]] goes crazy and becomes a psycopath after [[spoiler: Katey]] dies.
* In Season Two of ''Videogame/TheWalkingDead'', it is shown that [[spoiler:the group that the protagonists of the 400 Days DLC can possibly join is none other than Bill Carver's group. However, Bonnie ends up helping Clementine and her group escape Carver and ends up going with them by the end.]]
* In ''VisualNovel/SuperDanganRonpa2'' [[spoiler:BigBad Junko Enoshima attempts to convince the survivors that Makoto Naegi, TheHero of the first game has fallen victim to this.]] He hasn't.
* Though calling [[WildCard Ada Wong]] a "good" guy is being rather generous, she was never as outright heinously evil as she is in ''VideoGame/ResidentEvil6'' where she mercilessly infects the same soldiers who protected and escorted her to safety [[ForTheEvulz just for kicks]] and is soon discovered to be the leader of a [[NebulousEvilOrganization NEO Umbrella]] that plans to [[TheEndOfTheWorldAsWeKnowIt destroy the world]]. [[spoiler:It's revealed that Ada is actually [[EvilTwin a woman named Carla Radames]] and the ''real'' Ada is still the same [[DeadpanSnarker snarking]] [[DatingCatwoman Leon-loving]] AntiVillain she always was and is actively working to stop Carla.]]
* ''VideoGame/KnightsOfTheOldRepublic'':
** In the first ''Knights of the Old Republic'', Master Vrook is a character who many players saw as a grumpy, grouchy old man. In truth, he only acts this way if the player takes dark side options. If they play light side and talk to Vrook, he'll compliment them on their actions. By the time of [[VideoGame/KnightsOfTheOldRepublicIITheSithLords the sequel]] however, {{Flanderization}} sets in and he just hates you regardless of how well you act.
** By the time of ''VideoGame/StarWarsTheOldRepublic'', Revan, the protagonist of the first game, has clearly gone insane from his 300 years of captivity. At first, he takes over an old battle station and cooks up a plan to [[OmnicidalManiac wipe out 98% of the Imperial population]] (and likely, a good chunk of the Republic's population in the process). Then he returns, waging war on both the Republic and the Empire as the leader of a fanatical cult.
* A minor example in ''VideoGame/FarCry4''. CIA agent Willis Huntley, a major character around the mid-point of [[VideoGame/FarCry3 the previous game]], shows up again to give new protagonist Ajay a couple missions. These missions turn out to be [[spoiler:eliminating other CIA assets in the area to remove evidence of the CIA's presence in Kyrat, after which he throws Ajay out of his plane, leaving him to be captured by the guards of the person whose lieutenants (the aforementioned other CIA assets) he just killed.]]
* In ''VideoGame/TimeCrisis'', Robert Baxter was one of the player characters in the second game. [[spoiler: Then in the fifth, he becomes the BigBad.]]
* ''VideoGame/DawnOfWar 2: Chaos Rising'' introduces the Chaos faction, as well as a KarmaMeter that determines which of your characters is slowly falling to Chaos. [[spoiler:If you keep everyone pure, the traitor will be the MissionControl guy, but canonically Avitus turns traitor.]]
* ''Franchise/TheElderScrolls'':
** Hermaeus Mora, Daedric Prince of [[KeeperOfForbiddenKnowledge Knowledge]], in ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]''[='s=] ''Dragonborn'' DLC. In previous appearances, including vanilla ''Skyrim'', Mora is always a neutral entity, though he could be a bit ruthless in achieving his goals. In ''Dragonborn'', he [[TheChessmaster orchestrates everything that happens]], putting millions of innocent lives at risk, just to obtain the "secrets" of the [[NobleSavage Skaal]].
** In a case of sudden ''prequel'' heel syndrome, Sheogorath, the Daedric Prince of [[MadGod Madness]], is ''much'' more malevolent and sinister than he ever was before in ''VideoGame/TheElderScrollsOnline''[='s=] Mages Guild arc.
* ''Franchise/MassEffect'':
** While Donnel Udina is never a ''[[CorruptPolitician likable]]'' character, he is at least consistently presented as an advocate for humanity, and receives several PetTheDog moments in ''VideoGame/MassEffect3'' after the invasion of Earth, which makes it all the more surprising when [[spoiler: he turns out to be TheMole for Cerberus and helps with the attempted coup on the Citadel]], although it's implied he did so out of desperation following the invasion.
** The Illusive Man is the founder of the NGOSuperpower Cerberus that performs all manner of mad science experiments to ensure humanity's survival. While Cerberus was presented as villains in the first game through their unethical experiments, in the second they bring Shepard BackFromTheDead and prove themselves to be [[WellIntentionedExtremist well-intentioned extremists]] by explaining their previous actions and doing everything they can to help him/her stop the Reapers. However by the third game, [[spoiler: [[JumpingOffTheSlipperySlope they turn into full-blown villains]] due to the Illusive Man's indoctrination by the Reapers and perform actions such as killing civilians, attempting to provoke a war between the Turians and Krogan, attacking the Citadel, hunting down former members, and turning people into Husks]].