Face–Monster Turn

"Ma-ya... hurry... run! Before... I change...!! Hur... rry..."

— Ulala Serizawa, just before transforming into a Joker, Persona 2: Eternal Punishment

Basically this is when one of the good guys becomes a villain not out of choice, but because they were transformed into one one way or another (this makes it a supertrope to several tropes as outlined below). This can also apply to non-sapient entities, such as computers that go nuts, mons that are Turned Against Their Masters because someone else is giving them orders, and so on. As long as it was happy with its allegiance and something other than its own whims changed it, it fits. Subtrope of Was Once a Man.

Subtropes include:

• And Then John Was a Zombie
  When a protagonist who has been fighting monsters is literally transformed into one such monster (assuming their allegiance changes).
• Being Tortured Makes You Evil
  When someone is tortured until they join the side of their torturers.
• Brainwashed
  When someone with a different allegiance takes control of someone's mind, making them do their bidding.
• Brainwashed and Crazy
  When brainwashing is used to turn a person to violence against their former friends.
• The Corruption
  When a force of evil gives its victim superpowers while it mutates them into a monster.
• Cybernetics Eat Your Soul
  When replacing body parts with machinery causes a living person to lose their humanity or face other drawbacks.
• Demonic Possession
  When something else with a different allegiance hijacks the subject's body.
• Eldritch Transformation
  A character is transformed into an Eldritch Abomination.
• Main Character Final Boss: The main character becomes the final boss either of their own volition or as part of the main villain's machinations.
• Many Spirits Inside of One
  When multiple beings hijack a subject's body at the same time.
• More than Mind Control
  When brainwashing together with other factors changes someone's personality or allegiance.
• Murder Into Malevolence
  When a good or neutral person rises from an untimely death as an evil undead entity.
• Personality Remnant
  When a transformed person is still influenced by some of their original personality or attachments.
• Possession Burnout
  A possessed host's body suffers damage and decay that may quickly destroy it from being possessed.
• Psycho Serum
  A serum that gives a person powers also messes him or her up psychologically.
• Reforged into a Minion
  When the character is turned into one of the villain's minions.
• Resist the Beast
  When they try their hardest to stop the inevitable monster from emerging and resist the urge to kill, and warn others around them to stay away lest they face their doom.
• Self-Perception Shapeshifting
  When believing themself a monster physically transforms them into one.
• Split-Personality Takeover
  When a different personality starts calling the shots.
• Superpowered Evil Side
  For when a different personality is more powerful when it's in control and a little more interested in co-habitation (or at least can't get rid of the "face" personality).
• Tragic Monster
  When this happens either to someone the hero knows and/or cares about, or a backstory is given in such a way that their loss of humanity is to be seen as tragic.
• Transhuman Treachery
  When the original personality is still there, but their allegiance and morality has been warped with their form.
• Transformation of the Possessed
  When demonic possession also involves transforming into a demonic appearance.
• Unwilling Roboticisation
  When the person is forcibly turned into a robot or other machine.
• Vampire Refugee
  When the character fights their transformation and hopes to find a cure before it overtakes them completely.
• Villain-Possessed Bystander
  When the villain transforming random people into minions is a common occurrence.
• The Virus
  When the cause of the transformation is being "infected" by the enemy.
• Viral Transformation
  When a transformation that physically changes humans to non-humans can be spread virally.
• With Great Power Comes Great Insanity
  Being corrupted by an increase in power.
• Zombie Infectee
  Where this trope could occur at any moment.

Aversions and Subversions:

• Emergency Transformation
  When the transformation is induced to save a character's life. These characters can change alignment, but not all do.
• Heroic Willpower
  Through sheer willpower, love and loyalty the character maintains their Face status.
• Pro-Human Transhuman
  Despite no longer being human, the character still sympathizes with humans.
• Sheep in Wolf's Clothing
  When they use their transformation to aid their fellow humans.

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Examples:

Please only put examples here that don't fit into any of the above subtropes.

Anime and Manga

• In the Zanpakuto Tales filler arc of Bleach, the shinigami's Living Weapons are given human forms (turning them into something closer to Equippable Ally) and brainwashed with More than Mind Control into fighting them. The following arc deals with clearing up all the "sword beasts" (Zanpakuto who killed their shinigami before being turned back and went rogue).
• In Cute High Earth Defense Club LOVE!, the villains are able to turn normal students from the protagonists' school into the Monster of the Week by corrupting them when they're angry about something.
• In Delicious in Dungeon, this happens to Falin. She gets mutated into a harpy-like monster by the Big Bad, and can likely never be human again. She can, however, be close as possible... maybe.
• In Demon Slayer: Kimetsu no Yaiba, Zenitsu almost has this happen to him. He was once bitten by a spider which was to go on to mutate him into a mindless demonic human-spider hybrid and a minion of the Older Brother Spider Demon. He was saved by Shinobu and eventually had his shrunken limbs restored to normal. Later in the series, however, actual examples are shown, first the Upper-1 of the Twelve Kizuki, Kokushibo, is revealed to be a former Demon Slayer of the 1500's, older twin of the legendary Yoriichi Tsugikuni, who betrayed the Corps out of immense jealousy, insecurities and fear of death; then Kaigaku, Zenitsu's former elder colleague in Thunder Breathing, lost a fight to that same Kokushibo and was offered the same path of betrayal, he takes it. In the end, the last tragedy is Tanjiro himself turning into a demon, however, he was forced into it, and everyone alive focused their efforts on curing him then and there before it became an irreversible situation, thankfully Tanjiro is brought back fast enough.
• In Fairy Tail: 100 Years Quest, after being defeated and captured by the servants of the Moon Dragon God, Selene, Natsu and Gray are brought up to entertain Selene and her court, while Happy, and the girls of the team, are all transformed into cruel, predatory yokai, who barely remember their own identities, and have no qualms trying to kill either of the boys.
• In One Piece, it's implied this happens to Bartholomew Kuma as he turns more and more into a Pacifista, to the point that he says that he will technically die soon since his free will shall be taken away from him by the World Government. Though only a handful of people like Dragon, Ivankov, and Sabo, his fellow former Revolutionaries; and Bonney his adoptive daughter and her crew (and his friends in Sorbet) are aware that Kuma was ever not a monster.
• In Puella Magi Madoka Magica, this happens to Sayaka and any other Magical Girl whose Soul Gems don't get purified.
• Soul Eater:
  • This happens to Death the Kid while trapped in Eibon's book.
  • The whole Dark Side of the series is made of 'madness' and its effects.
• In YuYu Hakusho, Urameshi Yusuke pretends that this (v.1) has happened when he comes back from the dead the second time, just to mess with the racist assholes from the Spirit World who'd been sent to vaporize his corpse to make sure he couldn't arise as a superpowered demon. The dub version ends his Face–Heel Turn speech with "PSYCH!", and in all versions, he puts a shoe on his head and sticks his tongue out. Very funny. It works, and also freaks out Koenma very badly (to a My God, What Have I Done? level for a couple of seconds over protecting the corpse), as well any readers/viewers who couldn't keep ahead of the plot and predict the crazy man.

Comic Books

• In Amulet, this often happens to Stonekeepers who draw too much on their Amulet's power and become overwhelmed by it in the process, or fall prey to the manipulations of the Amulet spirit. Particular mention goes to Emily in Firelight, who turns into a giant, flaming phoenix.
• The Batman Vampire trilogy basically sees this happen to Batman after he is transformed into a vampire, his determination to continue acting as a hero eventually faltering as he succumbs to the thirst for human blood, only able to control himself just enough so that he doesn't kill innocent people but only targets Gotham's existing criminals.
• Bruce Banner when he turns into The Incredible Hulk, particularly in the original comics, in which the Hulk starts off as a power-hungry sociopath who almost considers killing a teenager who knows who he really is.
• Revolutionaries: After he dies, Domitius Major is reanimated by the Talisman... as a nightmarish Worm That Walks zombie that attacks anything the Talisman tells it to.
• Spider-Man: Curt Conners is by all accounts a good man: devoted husband and father, brilliant scientist, and dedicated to helping amputees... by developing experimental lizard gene therapy that turns him into the Lizard.
• Poisons in Venomverse and its sequels operate by infesting symbiote hosts, which turns the host and symbiote into a Poison connected to the Hive Mind. Characters who are very mentally powerful (Jean Grey) or just plain bonkers (Deadpool, Carnage) are shown to have a degree of resistance to it, but the majority of characters who are infested turn almost instantly.

Fan Works

• In the final act of Among Us in Character, Drama is taken over by an alien parasite that twists her body and mind and uses her to go after the remaining crewmates.
• Kingdom Hearts: The Antipode: In the fourth installment, All That's Left, Elsa is stabbed in the heart with a shard of enchanted glass, forcefully corrupting her and making her see only the ugly in the world (a reference to the original fairy tale).
• The RWBY fic I Can Almost Hear The Hounds naturally deals with this, given that the premise is that Ruby was taken and turned into a Hound.
• In The Myth of Link & Zelda: Breath of the Wild, it's revealed when Link draws the Master Sword that Ganondorf/Ganon was meant to be a hero fighting alongside Link and Zelda. All three of them were meant to fight Demise's curse over generations, each incarnation growing stronger and stronger until they finally could wield the full power of the three spirit animals, the Boar for Ganondorf, the Wolf for Link, the Owl for Zelda. However, Ganodorf was possessed and corrupted by that very curse. This imagery is symbolized in a vision by the originally beautiful magenta Boar Spirit suddenly turning dark and filling with black until it became Calamity Ganon.
• In Shattered Skies: The Morning Lights, Sailor Jupiter is hit with an Evil Nut and turns into a Pseudo-Witch, Mami Tomoe and Kyoko Sakura are forcibly transformed into "Witch-Hybrids", halfway between their human and Witch forms, and Cure Fortune is assimilated by an upgraded Droid Jamanen via horrific Orifice Invasion, which converts her into a "drone" Slime Girl under Jamanen's total control.

Films — Animated

• Aladdin: When Jafar finally gets his hands on the lamp, thus controlling the genie (who has to obey his evil master even though he doesn't want to harm Aladdin).
• Vakama in BIONICLE 3: Web of Shadows. While he was shown to be on shaky terms with his team even prior to his mutation into a half-beast, he only turned evil due to Roodaka taking advantage of his bestial impulses.
• In We're Back! A Dinosaur's Story, when the dinosaurs sacrifice themselves to be part of Dr. Screweye's circus to allow the kids to go free. They get scary looking too...

Films — Live-Action

• In Indiana Jones and the Temple of Doom, Indy is made into a zombie-slave, though he later recovers.
• In Resident Evil: Apocalypse, a hero from the first movie is turned into Nemesis and sent to fight Alice and the heroes. Eventually she does manage to reach him and get him to break their control.
• The clone troops who are forced to turn against the Jedi by an implanted command in Revenge of the Sith.
• In Street Fighter, this is the goal of Bison's Super-Soldier program, starting by turning Guile's friend Blanka into a green monster. Thankfully, while he was being brainwashed the scientist in charge switched the "Evil" off and turned the "Good" on, allowing for a 40 / 60 % mix of Evil to Good, respectively (more or less, it's been a while).
• In Van Helsing, the titular character gets bitten by a werewolf and turns into one. Although he fights and ends up killing Dracula, he is still a monster and ends up killing his female companion before she can cure him.

Literature

• The Empirium Trilogy: Eliana's mother was a genuinely good parent who only wanted to keep her children safe from the Undying Empire. Upon being abducted by Fidelia, though, she underwent a transformation into a crawler, a not-quite-human beast. She manages to retain a bit of her humanity at the last minute when she asks Eliana to kill her.
• Fate of the Jedi: Abeloth after she drank from the Fountain of Power and took a bath in the Pool of Knowledge to be like the Ones.
• Vampire Academy:
  • In Vampire Academy, Natalie turns Strigoi in an attempt to get her father out of jail.
  • Dimitri is turned Strigoi against his will at the end of Shadow Kissed.
• The Witchlands: Kullen turns on his former friends after he Cleaves.
• In WorldEnd: What Do You Do at the End of the World? Are You Busy? Will You Save Us?, this eventually happens to the main character after he starts turning into one of the 17 Beasts. While still able to exert some control over his actions, it’s a losing battle, and he inevitably becomes the final antagonist of the series.

Live-Action TV

• Subverted, inverted and played straight in the case of Angel from Buffy the Vampire Slayer and Angel: he was a jackass who was turned into a monster, was forcibly given back his soul and instead of returning to his jackass original personality, became a good guy, who was then turned back into a monster, and back into a good guy several times. It's the reason why he doesn't go by his former human name even when he's a good guy; he's not that person anymore. By the time he gets cursed with a soul, he'd been a vampire for about five times longer than he was ever human. He still considers himself a monster, just one capable of feeling guilt for his actions.
• In Charmed (1998), it becomes a Running Gag how often each of the girls gets transformed into a wendigo/vampire/demon/Fury and has to be saved by the others. (They also turn into good creatures a lot, too.)
• Highlander: Immortals can be corrupted by absorbing to much evil from the quickenings of wicked immortals and in turn pass on that corruption in the form of a dark quickening. Duncan is only known immortal in the canon of the TV show to overcome being turned by one.
• Kamen Rider:
  • In Kamen Rider Kiva, a villain turns Wataru into a scary-looking CGI monster and brings him under his control. He eventually breaks free and uses the monster form to kick his would-be master's ass. We see "Kiva Emperor Flight Style" only once more after that, sadly.
  • In Kamen Rider Gaim, while Hase isn't a face, he's an ineffectual antagonist and one whose antagonist status comes out of innocent bickering between dance teams rather than genuine malice. As soon as his Driver is broken, however, he loses his protection from the compulsion to eat the fruit of Helheim, and shortly thereafter demonstrates that anyone who succumbs to the temptation is transformed into a mindless monster. He also, however, demonstrates that having worn a Driver makes the transformation take noticeably longer and leave more of the human intact, and Kaito later uses this same process to his advantage in order to ascend to the position of Big Bad by taking on a very powerful, very intelligent monster form.
  • In Kamen Rider Geats, Michinaga flirts with this trope by using a Jyamato Buckle when he turns heel, which he's warned will turn him into a plant-based monster with enough usage on top of how overusing his existing powers have already turned him into a zombie. However, Michinaga successfully wins the Jyamato Grand Prix before he can actually turn into a monster, and wishes himself back to full health alongside gaining a new powerup that's far better than the Jyamato Buckle. He turns face again shortly afterward. Daichi, meanwhile, does go through with turning himself into a Jyamato, but turns face near the end of the show while keeping his new Monster Lord form, thus turning all the Jyamato face along with him.
• Power Rangers:
  • This happens to civilians on an "a few times in some seasons" basis. A person is turned into a Monster of the Week, and acts like a Monster of the Week until he is freed. Whether blowing up the monster form with a Finishing Move will free the person or is something that would kill him so the Rangers have to come up with something else varies (though in Power Rangers: Dino Thunder, kaboom always works).
  • In Power Rangers RPM, Dillon has cyborg implants that occasionally try to take over. In the finale, it is revealed that this also applies to half the city.
• Star Trek:
  • Star Trek: The Original Series:
    • In "The Return of the Archons", Sulu is turned into one of Landru's followers.
    • In "Catspaw", some of the crew are made into zombie-slaves by the witch-alien.
  • Jean-Luc Picard is turned into Locutus of Borg in the Star Trek: The Next Generation episode(s) "The Best of Both Worlds".
  • In the Star Trek: Voyager episode "Equinox", the captain of the titular ship deletes the Doctor's ethical subroutines, and then has him essentially torture Seven of Nine.
• Supernatural:
  • Sam undergoes this in Season 6 due to Castiel accidentally resurrecting him without a soul.
  • Dean is transformed into a demon by the Mark of Cain in the Season 9 finale, and remains so for four episodes before being cured.

Mythology

• This happens often in Classical Mythology, as looking like a monster is apparently synonymous with being evil. Scylla and Medusa are both well-known examples: women who were cursed for things that weren't their fault and became vicious and destructive as a result.

Professional Wrestling

• The (indirect) Trope Namer here would likely be Fighting Opera Hustle, in which the main Power Stable, the Takada Monster Army, set out to destroy professional wrestling using an army of Wrestling Monsters and brainwashed professional wrestlers, turning them into monsters for its cause. Not even Genichiro Tenryu, the most stubborn practitioner of tradition puroresu who had gone toe to toe with shooters of all kinds, was immune!

Theater

• Tamamo-no-Mae Asahi no Tamoto: Lady Hatsuhana a.k.a. the titular Tamamo-no-Mae was a decent woman chosen to become the Emperor's concubine before she is possessed by an evil fox spirit for no apparent reason. She then sides with Prince Usugumo to start a coup against the Emperor and take over the country.

Video Games

• Ao Oni, specifically, version 6. Takeshi even tries to kill himself to avoid this. It doesn't work.
• While not on the "Good" side, the scientists turned into purple spider-zombies in Azure Striker Gunvolt possibly count.
• Cave Story: The Doctor feeds red flowers to one of your allies, turning her into a frenzied monster and forcing you to kill her. Near the end, he also transforms your friend Sue and his minion Misery into monsters to help him in the fight (Sue gets better; Misery's fate isn't explored, but she was apparently able to send Balrog to help you escape from the Bonus Level of Hell).
• In Disney Princess: Enchanted Journey, the Bogs are actually captured butterflies that were forced into evil, and return to their natural state once defeated.
• Dragon Quest:
  • Togres from Dragon Quest VII, according to their Dragon Quest X bestiary entry, were once heroes who stole Kazapstrophe from the gods but were turned into monsters by them as punishment.
  • From Dragon Quest X itself, Zombie Paladins were once Paladins who protected the people, but became minions of Jagonuba after they were betrayed by the very people they protected.
• The penultimate boss in Freedom Planet is Milla, who has been corrupted by Lord Brevon into a monster. Lilac or Carol is forced to kill this character in order to advance (or so it seems; Milla survives, but just barely). However, playing as the spoiler character skips this boss battle entirely, since the character can't fight themselves.
• In Mother 3, Lucas's twin brother Claus (who was either seriously injured or dead) is turned into a cyborg and mindless slave by the Pigmask Army. However, we know he's in there.
• Persona 2: Eternal Punishment provides the page quote above. For context, Ulala, one of the main heroes, drunkenly invokes the JOKER Curse on Maya by calling her own phone number (which summons a serial killer to try to murder whoever the caller wishes) during a moment of weakness over her inferiority to Maya's success. Unfortunately, later in the game, the villains cause anyone who's called the number to turn into a JOKER themselves — Ulala is not immune to this, and Maya, Katsuya, and Baofu have to fight her to free her.
• In Quake IV, the Player Character is Stroggified, but his comrades rescue him before his mind control chip can be activated, thus making him a Phlebotinum Rebel.
• This is what André really is in Rayman 3: Hoodlum Havoc: a red lum who got scared, turning it into an evil black lum.
• Resident Evil:
  • Brad Vickers survives the first Resident Evil just to show up in Resident Evil 2 as an optional zombie encounter. 3 shows how he was zombified.
  • In Resident Evil – Code: Veronica, Steve is infected with T-Veronica and attacks Claire until The Power of Love returns him to normal (but he dies immediately after).
  • In Resident Evil: Outbreak File #2, the third series Tyrant helps the players at first (since it's been programmed to protect humans and destroy hunters). Then it gets damaged, loses its Power Limiter, mutates even more and goes crazy. Also, if a player dies, they turn into a zombie (or a more powerful Roaming Enemy in one level).
• In Shadow Hearts: From The New World, Edna Capone suffers from this after being revived with the power of Malice.
• Soul Series: Already teetering on the edge of being utterly mental, Tragic Hero Siegfried Schtauffen in the original Soul Edge is completely consumed by the eponymous Evil Sword when he finally takes possession of it, turning him into the Soul Edge manifest; a rampaging demon-knight known as Nightmare.
• Every single enemy bar the final boss in Wario Land 3 turns out to be a human turned into a monster by the Big Bad as revenge for sealing him away.
• In Zenonia 3: The Midgard Story, Ekinard's toxin leaks into the rivers on Maru Island and causes anyone who drinks the water to turn into a monster.

Western Animation

• The Batman: Police detective Ethan Bennett gets accidentally turned into Clayface by the Joker, and he goes back and forth between being a good or evil character throughout the series.
• Generator Rex: Being mutated into an EVO can have this effect if the victim is severely unlucky. Most formerly-human EVOs can keep their minds if they remain humanoid, but others become feral and animalistic, don't recognize friends from foes, and in the worst cases, start eating people. Van Kleiss eventually gains the ability to create EVOs loyal to him by activating the nanites in unmutated life forms, with their new allegiance signified by a yellow handprint left where he touched them.
• In Miraculous Ladybug, the main villain, Hawk Moth, has the power to turn normal people into the Monster of the Week by preying on them in moments of anger or depression. One of Ladybug's powers is to purify the akumas that possess them, turning them back to normal.
• This happened in the Backstory of Steven Universe. Those monsters the Crystal Gems are always fighting? They're other Gems. At the end of the Gem War, Homeworld deployed a Fantastic Nuke that mutated and corrupted every Gem caught in its range. Pearl, Garnet, and Rose were the only Crystal Gems who escaped it, and they spent most of their time since capturing their former friends and enemies to stop them from hurting people.
• In Steven Universe: Future, of all people, Steven himself suffers one of these during his mental breakdown in the episode "Everything's Fine". His self-hatred, combined with his unchecked PTSD, feelings of purposelessness, and his uncontrollable powers, corrupted him and turned him into a pink Kaiju-like monster. He gets better at the end of "I Am My Monster".
• Transformers: Animated:
  • Blackarachnia actually turned to the side of the Decepticons after mutating into an organic spider.
  • Wasp also became a Decepticon after Blackarachnia mutated him into an organic wasp shortly after he vowed revenge on Bumblebee for (accidentally) sending him to prison, though he'd been trying to take Bee down for some time before. The Decepticon symbol his new form inexplicably has is basically there 'cause the toy has it.
• In W.I.T.C.H., Nerissa creates two additional Knights of Destruction as her minions, turning Matt (Will's boyfriend) and Mr. Huggins (Matt's pet dormouse) into Shagon and Khor, respectively. Most of the time, the girls aren't aware that Shagon and Khor are actually their friends turned into evil monsters.

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