A Pupil of Mine Until He Turned to Evil

aka: A Pupil Of Mine Until She Turned To Evil

"Why do I get the feeling you're going to be the death of me?"

"Shifu found him as a cub and raised him as his son. And when the boy showed talents in kung-fu, Shifu trained him. He believed in him, he told him he was destined for greatness. It was never enough for Tai Lung. He wanted the Dragon Scroll, but Oogway saw darkness in his heart and refused. Outraged, Tai Lung laid waste to the valley. He tried to take the scroll by force and Shifu tried to destroy what he created... but how could he?"

— Tigress about Tai Lung, Kung Fu Panda

A mentor once had a student, who used to be a good person, and perhaps the mentor's most promising and skilled student ever. That student had a flaw; a seed of villainy that needed a trigger. Usually, it was arrogance about his/her skills, or impatience at not being taught the final skills that the mentor had yet to teach. Then the student became a villain.

Sometimes the mentor is a Hero Protagonist and will have to take the student down in the story, resulting in an Older Hero vs. Younger Villain scenario. More often, the protagonist is another student the mentor takes on. If that's the case then the other student is the Mentor's New Hope and the former student is a Hero's Evil Predecessor. A long enough Master-Apprentice Chain might include a story of one of these as a precautionary tale.

Compare Deceptive Disciple (when the student was evil the whole time, just pretending not to be), Evil Former Friend, Fallen Hero, Merlin and Nimue, Sixth Ranger Traitor, Used to Be a Sweet Kid, and The Paragon Always Rebels.

Contrast Treacherous Advisor, which is when the mentor betrays the student.

Not to be confused with Hellish Pupils. This is "pupil" as in a student, not part of an eye.

Do not put examples unless it was clearly stated the pupil was good beforehand. If it turns out the pupil wasn't, that's Deceptive Disciple.

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Examples:

Anime & Manga

• Demon City Shinjuku. Levih Rah was once the student and ally of his master Agni Lai, who taught him the art of Nempo. Unfortunately he was envious of the power of other men and ended up selling his soul to the demons of Hell in return for vast power.
• In Demon Slayer: Kimetsu no Yaiba, Kaigaku was the student of the former Thunder Hashira, alongside Zenitsu Atsaguma. Although it's arguable that he's always been evil, as he was known for his arrogance, jealousy, and cruelty, and he frequently berated Zenitsu for his closeness to their master and his cowardice. Kaigaku eventually became a demon, pledging his loyalty to Muzan Kibutsuji, in order to save himself from dying to Upper Rank 1, Kokushibo. He later became the Upper Rank 6 of the 12 Kizuki, following the death of the former rank holder. In order to take accountability for Kaigaku's fall, their master committed seppuku, much to Zenitsu's fury and despair.
• Dragon Ball:
  • In Dragon Ball, the Master Roshi states that Master Shen used to be a fellow student of the mighty Mutaito, who underwent a Face–Heel Turn after seeing the might of Demon King Piccolo, having apparently decided that Being Good Sucks.
  • In Dragon Ball Super, Zamasu is Gowasu's student, chosen to become the next Supreme Kai of Universe 10. However, Zamasu's black and white views on mortals cause him to see the beings he's suppose to guide and protect as being unworthy of the gods' knowledge. Meeting Goku and going to Planet Babari only solidified his bias, and concludes that all mortals need to be wipe out for universal peace. To that end, Present Zamasu tries to murder Gowasu and steal his Time Ring. When Gowasu was told of this, he is definitely not pleased. The Zamasu who would become Black not only killed his master for the earrings, but also killed Future Gowasu.
    • The same can be said for Goku Black, since he is actually an alternate Present Zamasu who succeeded in murdering his master Gowasu.
• Fullmetal Alchemist pulls a variation, in that Homunculus kind of mentored Slave #23 from the day he gave him his name...but recognized Van Hohenheim as "his father." Given his entire identity is later molded around the fatherly role, this concept is clearly significant to him.
  • Thus Hohenheim's part in the finale manages to combine the mentor role here with Calling the Old Man Out. Ed gets to be the third link in the chain when they off his big brother.
  • The first anime played with the trope in that Ed's master Izumi Curtis had trained under an old woman named Dante, who turned out to be the villain.
• Naruto:
  • Orochimaru was the Third Hokage's student, considered the village's best ninja when he was in Konoha and 'good' enough to cry when Dan died. Then got fed up with things and left for his various evil deeds. The Third Hokage notes that he always suspected something was amiss about Orochimaru, so it's unclear when exactly he turned evil, even if he was evil before he left the village (around the time the Third Hokage chose Minato for the position of Fourth Hokage largely because Orochimaru was untrustworthy.)
  • There's also Sasuke, Kakashi's former student who abandoned the Leaf Village to train with Orochimaru, and then goes on a Roaring Rampage of Revenge once that's done. At one point he even allies himself with Akatsuki. Even after his talk with Hashirama, he still planned on killing all the Kages and taking over the Leaf Village after the war was over, requiring Naruto to beat even more sense into him.
  • There's also Nagato, also known as Pain, a former apprentice of Jiraiya. More of a Well-Intentioned Extremist, but he still qualifies because he puts such a heavy emphasis on the "extremist" part. Especially since his 'good intention' is to invent a chakra nuke and use it so that everyone will be too afraid to go to war for a few generations.
  • Danzo could also be considered sort of an example, as he used to be a student of the 2nd Hokage. While not strictly evil as he thinks his actions are what's best for the village, he's pretty much constantly doing morally questionable things and getting involved in Dirty Business.
  • Then there's Obito, who became Tobi, the leader of Akatsuki and Dragon-in-Chief to Madara Uchiha. Like Orochimaru and Nagato, he played a big role in the death of his former teacher, Minato. However, unlike most examples of this trope, his teacher never knew that he had turned evil, or that he was even alive. Minato is legitimately shocked to realize Tobi and Obito are one and the same after he's revived by Edo Tensei during the Fourth Shinobi War and teleports in to cut down Obito, and blames himself at least in part for not being there to save him from falling down his path.
• One Piece: This is inverted with Trafalgar and the Donquixote Family. The Donquixote Family served as Evil Mentors to Law when he was 10 to 12 years old, and he hoped that the skills and strength he was earning would turn him into a ruthless killer like Doflamingo himself. Swordsmanship from Diamante, marksmanship from Gladius, martial arts from Lao G, and further academic education from Doflamingo. Doflamingo intended Law to become his right-hand man in the future, but thanks to Corazon course correcting the young Law and getting him out of the crew, Trafalgar Law became a good person instead (although still somewhat sadistic and ruthless). In the present time, Law is takes a significant part of ending Doflamingo's evil reign over Dressrosa.
• Garou from One-Punch Man was once the most promising student of Bang, the Master of the Water Stream Rock Smashing Fist and Rank 3 S-Class Hero. He then snaps one day, destroys the rest of the dojo, and begins hero hunting. Eventually he becomes so terrifyingly powerful that he could single-handedly destroy the entire S-Class, and is able to briefly tangle with Saitama. Subverted in that Garou was more of an angry teenager lashing out at "unfairness" than a true villain; he never really killed any of the heroes, although he did hospitalize a fair few.
• Rurouni Kenshin: The trope title is almost a word-for-word utterance by Old Man Okina after fully realizing that his most beloved disciple, Aoshi, has fallen entirely to the dark side — and is in league with Makoto Shishio, to boot. Specifically, he askd Kenshin to put an end to Aoshi's life. However, in a moment that also defies Broken Pedestal on Misao's part, Kenshin refuses to do it, he believes that Aoshi still possess a trace of goodness in his heart. A few hard knocks later, Aoshi realizes the errors of his ways.
• In Episode 10 of Samurai Champloo, the gang meets up with a friendly monk who turns out to have been a former martial arts teacher who once taught Shoryuu, the villain of the episode. He had encouraged Shoryuu to travel and hone his skills, but this went horribly wrong, when after learning an amazing technique, Shoryuu became obsessed with proving his greatness by challenging and killing any martial artist he could find.
• In Soul Eater, Asura was Shinigami's apprentice and as it turns out, son, by virtue of being one of his fragments alongside Death the Kid until he went insane (likely because he was created by Shinigami for the himself to purge himself of his own fears in order to become the "God of Absolute Order"^note As Shinigami is the Great Old One who irradiates Madness of Order, Asura as the embodiment of his fear ended up as a Great Old One who irradiates Madness of Chaos), became the very first Kishin and threatened to destroy the world, and had to be sealed away.
• Yu-Gi-Oh! GX: After his Freak Out, Kaiser Ryo Marufuji defeated his old mentor and stole one of those dangerous forbidden decks, but the sad part is Sameshima incorrectly thought he was in there somewhere.

Asian Animation

• Happy Heroes: The backstory of Shao Long, a character introduced in Season 2 episode 25, is that he was Headmaster Tele's favorite student at Superstar School and was taught all the Headmaster's tricks before turning to the dark side when he grew up out of a desire to be the best. Headmaster Tele, upon learning this, is devastated.
• In Kung Fu Wa Manipulens, the show's big bad, used to be Kung Fu Sock Master's student, but his thirst for power and impatience made him betray him and try to steal the Ancient Scroll, flashbacks show that he didn't cared for his master always wanted to become powerful.

Comic Books

• The Amazing Screw-On Head: A slight variation, as Emperor Zombie used to be Head's manservant until he turned to evil.
• Batman: Jason Todd, the second Robin who died and came back later wearing a different mask, although whether he wants to (lethally) simply stop all crime from Gotham or murder the whole Batfamily depends on the writer. Come the New 52, Jason has mostly made a Heel–Face Turn, though his relationship with the rest of the family is still strained and he's still prone to lethal force when sufficiently pushed.
  • Subverted in Batman: Last Knight on Earth, as over the course of the story, the characters speculate that Omega was a protege of the original Batman who went rogue and betrayed his ideals, but while technically the latter is true, Omega didn't betray Bruce — as it turns out that Omega is actually the original Bruce Wayne himself.
• Death Vigil: Inverted by Wulf, who was Sam's mentor in the Vigil. Wulf was a loyal and respected member of the Vigil for centuries, but then his gifted surrogate daughter was killed in an accident and Bernie was unable to do anything for her. Although we never hear her reasoning from Bernie's perspective, Wulf claims she refused him, and didn't take it well.
• Doctor Strange: It's not quite clear whether the Ancient One's other disciple Baron Mordo was this or a Deceptive Disciple. Maybe a little of both.
• The Quest For The Time Bird: Bulrog was a former student of the knight Bragon who turned mercenary and eventually ends up seeking vengeance on his master.
• Moon Knight: Jeff Wilde, the son of villain the Midnight Man, takes on the superheroic persona of Midnight and attaches himself as sidekick to the reluctant Marc Spector. The HYDRA breakaway sect Secret Empire capture him and subject him to Unwilling Roboticisation, causing him to turn Ax-Crazy.

Fan Works

• Better Bones AU: Cloudtail is no longer Ashfur's adoptive brother as in canon due to issues of avoiding incest in the Tangled Family Tree. Instead, he is now mentor to a younger-than-in-canon Ashfur to keep their dynamic as close to each other. They bonded with each other like most mentors and apprentices before Ashfur's Face–Heel Turn, and Cloudtail takes a leading role in rebelling against Ashfur when he possesses Bramblestar while trying to come to terms with how the cat he loved became so horrible.
• Child of the Storm has this tend to be a sign that Doctor Strange is not quite as infallible as he appears and lets everyone believe. In the sequel, he rather sadly states that he's only taken five students (four at the start of the story, the fifth being Harry) over his extremely long life, and only one — Wanda Maximoff - turned out well. Indeed, he says that he could not be more proud of her, and her success was more down to her virtues as a student than his as a teacher.
  • Mordo was this, though it's ambiguous, because his main impact (he hasn't appeared) is in his own choice of student — Victor von Doom. The sheer scale of manipulation and ruthlessness this version of Strange is capable of means it's possible that he actually intended for Mordo to fall (assuming that Mordo wasn't a Deceptive Disciple to begin with), in order to teach Doom in turn.
  • An unambiguous case is one of Strange's other students, revealed in the sequel to be Margaret Le Fay, mother of Harry Dresden. He took her in when she was seeking other viewpoints to the White Council's rigid stance of non-interference/focus on fettering magical power rather than using it to make a difference, teaching her how to handle Black Magic safely (figuring that she was going to experiment anyway), but she left after deciding that he was too cautious and more concerned with the future rather than the present, joining up with darker forces. While Strange had anticipated this, he was hoping she would only skim the surface without pulling a true Face–Heel Turn — and while she did pull a Heel–Face Turn in the end, it got her killed.
  • The last to be revealed was his first student, a young, sweet, and immensely talented mutant-mage back in the depths of prehistory, who a young-ish Strange saw as the great hope and answer to his search. He trained the boy and raised him as if he were his own, though the boy already had an adopted father with a very different outlook. Unfortunately for everyone involved, due to a combination of circumstances and several personal flaws, the boy ended up listening to his father, turning on Strange and almost killing him, before unleashing unparalleled devastation, killing the Queens of Winter and Summer (among many, many others). The name that young man took? Apocalypse.
• The Pieces Lie Where They Fell: Unusually for this trope, it’s the student herself who explains this rather than the teacher — Sunset Shimmer reveals she was once Princess Celestia’s personal student, until the Princess felt she wasn’t “worthy” and “forced her out”.
• Seventh Endmost Vision: The Second Class SOLDIER Luxiere was one of Tifa Lockhart's many students back when she was a 1st Class SOLDIER. When they run into each other in chapter 8, Tifa reaches out to him to join her and Avalanche in the fight against Shinra. Luxiere makes it clear that while he respects her, he chooses not to follow the morales she tried to instill in him. Reno lampshades this trope before the fight, fearing that like in the movies the evil pupil Luxiere will successfully defeat Tifa and go on to kill the ex-Turks trio, though Tifa points out she didn't teach Luxiere everything she knew.

Films — Animation

• Kung Fu Panda has the antagonist of two of their films:
  • In Kung Fu Panda, Tai Lung was not only Shifu's first pupil, but also his adopted son, who Shifu pushed to excel at all costs, believing that he was training him to be the Dragon Warrior. Unfortunately, this fostered an obsession and pride in Tai Lung that made him totally unworthy. Tai Lung's Face–Heel Turn was a direct result of this rebuke and their screwed up relationship.
  • In Kung Fu Panda 2, this can be said of Lord Shen and the Soothsayer, who raised him. In this case, Shen never actually attacks the Soothsayer (in fact, she's the only one who can get away with insulting him — repeatedly — without being killed), but that doesn't mean he'll listen to any of her pleas to stop his mad dreams of conquest.
• In My Little Pony: Equestria Girls, Sunset Shimmer is a former pupil of Princess Celestia (and Twilight Sparkle's predecessor in that role). When Celestia's tutelage did not turn out to be the easy path, she "turned cruel, dishonest and rebellious," abandoning her studies and pursuing power in more unsavory ways. Unlike most, she is redeemed and becomes one of the heroes from then on, eventually returning to Equestria to have a brief though touching reunion with Celestia.

Films — Live-Action

• Betelgeuse in the movie Beetlejuice, worked for afterlife case worker Juno before he became a "freelance bio-exorcist."
• The Vietnamese gangster in Big Stan was The Master's star pupil. From the moment The Master calls Stan "My second best pupil", we just know this trope is going to be invoked!
• Inverted in Bill & Ted's Bogus Journey, where it is Rufus's old teacher (even if for gym), De Nomolos, who turns to evil.
  "I worked within the system until I could stand it no longer.''
• In Child's Play (1988), series Big Bad Chucky was originally mentored in his Hollywood Voodoo by a man called Dr. Death, who in spite of his ominous name intended for Chucky to use said voodoo for... well, one struggles to think of any purpose for a Body Surf ritual other than abusing it willy-nilly, bit evidently Dr. D had one in mind. He becomes outraged when he learns what Chucky has done, but due to being Too Dumb to Live quickly comes down with a terminal case of death-by-voodoo-doll.
• Subverted in Dragonheart: Bowen thought this trope was in play, and blamed Draco for Einon turning evil. He eventually learned that Einon was always evil.
• Han, the Big Bad of Enter the Dragon, was a student at the Shaolin temple until he became an organized crime boss. Lee, a more loyal student of the temple, is sent to stop him.
  Lee: You have offended my family, and you have offended the Shaolin temple.
• In Halloween (2018), Dr. Samuel Loomis trained Dr. Ranbir Sartain to keep a watch on Michael Myers and keep him from escaping, but Sartain became obsessed with understanding Michael to the point of turning him loose and murdering cops just to see how he operates in the outside world.
• The plot of The Hunted (2003) involves Tommy Lee Jones's character being asked to hunt down his former pupil, played by Benicio del Toro, who has gone rogue.
• Marvel Cinematic Universe:
  • In Ant-Man, Hank Pym had mentored Darren Cross but Cross grew resentful that Hank was unwilling to share his research on the Pym Particles and is driven to get the same results from the Pym Particles to prove he was better than Hank, leading him to supply HYDRA with weapons.
  • In Doctor Strange (2016), Kaecilius, a pupil of The Ancient One, goes rogue and recruits followers, steals a page from the Book of Cagliostro, and attempts to summon Dormammu of the Dark Dimension.
  • Thor: Ragnarok inverts this trope with Hela and Odin's relationship. The pair once led Asgard in brutal conquest of the other nine realms side by side, but then Odin Took a Level in Kindness and wound up having to seal Hela away. So he was A Mentor of Hers Until He Turned Good.
• Inverted in The Mighty Ducks between Gordon Bombay and Jack Reilly.
• Tommy Gunn from Rocky V, who starts out as Rocky's loyal protege, but becomes bitter when the public sees him as Rocky's puppet, and joins with a sleazy promoter instead.
• Sniper The White Raven: Downplayed example: Ukrainian sniper "Raven" is a former schoolteacher, and notices his former pupil Ivan among a group of Russian separatist militia in the Donbas conflict. He still pulls the trigger.
  Cap: He made his choice.
  Raven: And I made mine.
• In The Sorcerer's Apprentice, Veronica, Balthazar Blake and Horvath were pupils of Merlin, until Horvath went rogue and betrayed them to Morgana LeFay.
• In Star Wars, Anakin Skywalker, who studied under Obi-Wan Kenobi, was a good man, if arrogant and quick to anger, until he was seduced by the dark side (specifically, by Palpatine, who promised him a way to save his wife from her imminent death). He wound up becoming the Sith lord Darth Vader and right-hand to Palpatine, and an enemy of the very man who trained him. Much of Luke's arc is him worrying if he will go down the same path.
  • The Trope Namer is a line in Star Wars Episode IV: A New Hope, about how Obi-Wan describes Darth Vader.
    Luke Skywalker: How did my father die?
    Obi-Wan Kenobi: A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi Knights. He betrayed and murdered your father.
  • Taken to the extreme in Revenge of the Sith, the third film of the prequel trilogy with Anakin Skywalker and Obi-Wan Kenobi. Over the course of the film, the two go from best friends (and to Anakin, a Parental Substitute) to attempting to kill each other.
  • Also inverted by Vader at the end of Return of the Jedi.
  • Mirrored in the prequel trilogy with Dooku, who was Yoda's pupil before his Face–Heel Turn.
  • And now gone full circle in The Force Awakens with Kylo Ren, one of Luke's students (and his nephew by way of Han and Leia, whose real name is Ben Solo), going to the Dark Side (in part thanks to his obsession with his grandfather, the Trope Namer), slaughtering his fellow students, and serving the First Order in an attempt to defeat the New Republic. Ren then kills Han. Then, things get worse in The Last Jedi, when Kylo decides to kill Supreme Leader Snoke and makes himself the new Supreme Leader.
• Clu from TRON: Legacy. He took Flynn's original programming for him too far, and warped it. The comic Betrayal, however, indicates that he probably wasn't all that good to begin with, and Flynn was just too distracted by the pressures of his life in the analog world to notice until it was much too late.
• In X-Men: First Class, the mutants all train together as part a CIA team to fight Sebastian Shaw, but Angel Salvadore decides to join the Hellfire Club shortly after she is recruited by the program. At the end of the film, Magneto and Mystique, after defeating Shaw, form the Brotherhood and become the new Big Bads, turning against Charles Xavier, whose ideas about mutant-human relations differ from the ones they have.

Literature

• The Darklord Lorthas, former student of High Wizard Aemon in Boundary's Fall. He's still not entirely bad.
• Scimitar from Constance Verity Saves the World studied under the same master as Constance — Master Chaput — before he killed him. Now he wants nothing more than to kill his master's favorite apprentice.
• This is discussed in The Inheritance Cycle. Neither of Eragon's teachers, Brom or Oromis, taught the Big Bad of the series, Galbatorix (Brom would have been too young being a decade and a half younger than Galbatorix). Oromis says he's glad for it because Galbatorix made sure to personally kill anyone that was involved in his teaching. However, Oromis did train Galbatorix's late right-hand man Morzan.
• Sauron, the principle antagonist of Tolkien's The Lord of the Rings trilogy, was originally a Maia who followed the Vala Aulë the Smith, and went by the name Mairon. Then he was turned to evil by Melkor a.k.a. Morgoth, the original Dark Lord, who made Mairon his lieutenant. During the First Age Mairon earned several new names from the Elves, among them "Sauron" ("the abhorrent one" in Quenya) and "Gorthaur the Cruel" ("abominable dread" in Sindarin). When Morgoth was defeated, Sauron essentially became self-employed and sought to dominate Middle-earth himself. He kept his smithing skills and freely used them for evil, as shown by his involvement in forging the Rings of Power.
• Played for Laughs in Ruler of the Magical Keys, where the pupil in question is a cat who learned only one spell –- the one that could turn anyone and anything into a mouse -– and just went on searching for a good supper and getting rid of evil dogs.
• Inverted in The Secrets of the Immortal Nicholas Flamel. William Shakespeare was a pupil of John Dee (the Big Bad of the series) but turned to good. Or at least, turned to an ally of the Flamels. How good this makes him is not that clear.
• A number of Luke Skywalker's Jedi students in Star Wars Legends end up eventually falling to the Dark Side. He's able to bring some of them back.
  • Kyp Durron, a young man in the Jedi Academy Trilogy purportedly even stronger in the Force than the Skywalkers, is seduced to the dark side by the ghost of the ancient Sith Lord Exar Kun and takes a leftover Imperial superweapon on a bloody rampage against the Imperial Remnant before the other apprentices destroy Exar Kun and Han and Lando are able to talk Kyp down. In later books, he becomes The Atoner.
    • Exar Kun (and his first Sith apprentice, Ulic Qel-Droma) were former Jedi themselves before they fell to the Dark Side. In the Star Wars universe, they're pretty much the original pupils turned evil.
  • Brakiss intended to be a Deceptive Disciple, but Luke believed he could be turned; Brakiss started Becoming the Mask until Luke put him through a test which horrified him and caused him to flee. Luke always believed that Brakiss could be redeemed, and in The New Rebellion parts written from Brakiss's point of view suggest that he'd like that, but it's not to be: Brakiss is on the receiving end of a Heel–Face Door-Slam courtesy of a surviving Imperial Royal Guard at the end of the Shadow Academy arc in Young Jedi Knights.
  • Dolph Kueller in The New Rebellion is never really clearly explained and dies at the end of his only appearance.
  • Alema Rar, debuting in The New Jedi Order: Star By Star, suffers a Cynicism Catalyst in the form of witnessing her identical twin sister being killed by a Yuuzhan Vong creature bred to hunt and kill Jedi, and becomes an advocate of purportedly un-Jedi-like tactics against the Vong (e.g. using leftover Imperial superweapons). In The Dark Nest Trilogy Luke ultimately expels her from the Order over her behavior, and she spends the trilogy as the Goldfish Poop Gang before being unceremoniously Eaten Alive by a critter. Except it turns out that she survived this, and spends most of Legacy of the Force half-insane and determined to take down Han and Leia.
• Subverted, then averted in the Warrior Cats prequels. Gray Wing acts as a mentor and father figure to Thunder, his nephew. The reason behind this is because Clear Sky Thunder's father was slowly turning into a cruel Anti-Villain. When Gray Wing allows Thunder to visit him, Clear Sky claims custody of his son, who was young and naïve, and decides to mentor him. Gray Wing is powerless against this, and fears that Thunder would be influenced and turn cruel. Averted when Thunder deserts and disowns Clear Sky, seeing the error of his ways. Clear Sky eventually regains his senses, and the (three sort of) make up.
• In The Witchlands, Evraine thinks this way of Aeduen, her former disciple, as she believes he was making good progress as a Carawen Warrior Monk before he joined Ragnor's side. This being said, this is a world of Gray-and-Gray Morality.

Live-Action TV

• Inverted with Master Eubulon in Kamen Rider Dragon Knight.
• In the Marvel Cinematic Universe series Moon Knight, it's revealed that Arthur Harrow was the previous Avatar of Khonshu, who gradually became disillusioned with his service to the god due to only being able to punish people after they had committed crimes. He subsequently pulled a Face–Heel Turn and began serving Ammit, who is willing to kill people who will commit evil rather and, thus, prevent it.
• Power Rangers:
  • Played word-for-word straight by Jarrod in Power Rangers Jungle Fury. Rio, his counterpart in Juken Sentai Gekiranger, follows roughly the same path, but there is no single trigger that causes him to switch: he simply becomes dissatisfied with the progress he's making under the good guys.
  • Gekiranger also had the three Kenma, precursor villains who turned on the founder of Beast Fist after their leader learned he was the *second* choice for successor. This led to the Kensei sealing them away until Rio and Mele let them out.

Pro Wrestling

• This was the dynamic between Bruno Sammartino and Larry Zbyszko in the early 1980s.
• The entire Nexus - except for Daniel Bryan - turned out to be this.
• Chief Jay Strongbow was always a face, while his protégé Tatanka had two heel runs.
• Both subverted and inverted ("a pupil of mine until I turned good") in the case of the two female members of The Invasion. In the partnership of Torrie Wilson and Stacy Keibler it was apparently the latter who was the junior partner, with Wilson giving Keibler a demeaning slap on the buttocks to get her moving just before their Bra & Panties Match against Lita and Trish Stratus. But instead of Keibler rebelling against her master, it was Wilson who saw the light, much to Keibler's disgust. By the time the Invasion angle was over, Wilson had established herself as WWE Divas' resident All-American Face - well, for a time, anyway - while Keibler became a successful heel manager and corporate saboteur. In effect, the Darth Malak to Wilson's Darth Revan.
• Ian Rotten helped Chris Hero, giving him the most recognition in his career till then in IWA Mid-South, as well as giving him some instruction to improve in wrestling. Hero would go on to turn on Rotten and all things IWA Mid-South just because of a loss to Arik Cannon.
• Tommy Dreamer found this after taking Colin Delaney "under his wing". This had no resolution in WWECW, as Delaney was released, but Dreamer has since had to deal with his misdeeds elsewhere, such as the International Wrestling Cartel.
• Mr. 450 turned on his teacher, Invader #3 in the World Wrestling League after Invader decided attacking Sensacional Carlitos after their Navida Corporativa match, after Carlitos had displayed good sportsmanship, was a step too far.

Tabletop Games

• Dungeons & Dragons:
  • Forgotten Realms setting. Elminster isn't really into it, but he taught a lot of wizards in his years, and the main requirement was the talent, not moral qualities — it's Mystra's priorities and not that her own avatars never were downright villainous. So... Sammaster — though after being "certified" by Mystra and before fully going nuts. The Shadowsil — became an evil archmage, worked in late Sammaster's little club, virgin sacrifices and all that. Raerlin — the guy has a dubious achievement of saying "Death has come for you at last, Old Mage" twice: once while alive, once as a lich. And so on, and on.
• In HeroQuest, Big Bad Morcar/Zargon was a student of Mentor who got fed up with not being taught magic fast enough, read texts forbidden to him in secret, gained great power, and ran off to become the Lord of Chaos.
• Horus in Warhammer 40,000 used to be the most trusted Primarch of the God-Emperor, who treated him like a son. Then Horus gets corrupted by Chaos and leads a rebellion that results in trillions dead, the Emperor in a coma, and the future of the Imperium in peril.

Video Games

• In the Jack the Ripper DLC for Assassin's Creed Syndicate, it's revealed that the eponymous ripper used to be a boy called "Jack the lad" who was being trained by Jacob to become an Assassin. Upon returning from a trip to India to study the Indian Brotherhood's fear tactics, Jack became disillusioned with Jacob's view of the Creed, instead believing that the Assassins should be publicly feared and should resort to killing innocents to maintain this fear. Evie ends up putting an end to his reign of terror after Jacob was unable to subdue his former apprentice.
• In Atlas Reactor, Old Master Su-Ren views Kaigin, who was formerly her student, this way. Given the Cyberpunk Grey-and-Gray Morality of the setting the truth is a little more complicated than that, but it's very clear that the two of them are not on the same side. In a slight deviance from the trope, Su-Ren never considered Kaigin her best student but rather the opposite.
• Baldur's Gate III: Archdruid Halsin feels responsible for Kagha's attempted genocidal purge because he was her mentor. The player can derail Kagha's plans either directly or by rescuing Halsin. If Halsin is rescued, he strips Kagha of her rank and publicly declares her a novice apprentice who needs to relearn the importance of harmony amongst all of nature's creatures.
• According to the manual for the original Banjo-Kazooie, Gruntilda the witch was a student of Mumbo-Jumbo's until she turned evil... and to pay him back, she turned his head into a skull-shaped metal mask. It seems to have been Ret Conned, though, with Grunty's Revenge (which takes place in the past) has Mumbo Jumbo as an up-and-coming shaman without a pupil... and a face that's still skull-shaped.
• Fatal Fury: Geese Howard was a student of Tung Fu Rue, alongside Jeff Bogard, the adoptive father of Terry and Andy. When the time came to pass on the greatest secrets of Hakkyokuseiken, Tung Fu Rue chose Jeff to learn them, infuriating Geese, who swore revenge and left the school. Years later, after becoming a powerful crime boss, Geese ambushed and brutally murdered Jeff Bogard, causing his sons to swear vengeance themselves and starting the entire plot of the series.
• Final Fantasy:
  • Xande, the Big Bad of Final Fantasy III, was once one of three students of the Great Sage Noah and hinted by various comments by Doga, his moogle and Unei in the 3D remake to have been a good man. However, when his master died, Noah gave him the gift of mortality. Feeling slighted and fearing his eventual death, Xande unleashed a flood of darkness upon the world in retaliation, with the remake introducing a time stop element, that Xande intended to use to delay his death which the Cloud of Darkness takes advantage of.
  • Vargas, in Final Fantasy VI, kills his father and master (though said master turns out to be alive after the Time Skip) out of the belief that he favored Sabin.
• In Final Fantasy XIV, the Samurai job questline entails helping the wandering warrior Musosai pursue a criminal named Kogarashi, whose crimes include mentoring a pupil who used his teachings to commit murder. Under Hingan law, a samurai must take responsibility for any and all crimes committed by their pupils. Eventually, Musosai reveals that he is Kogarashi before his final fight with the player. His pupil plays a bigger role in subsequent job quests.
• In the Fire Emblem series:
  • In the backstory of Fire Emblem: Shadow Dragon & the Blade of Light, Gharnef was once a pupil of Gotoh, the White Sage. However, when Gotoh passed the legendary magic tome Aura on to his other pupil Miloah because Gharnef, while a good man, lacked compassion, he was overcome by jealousy and stole the Darksphere, a cursed artifact that twisted him into the cruel Evil Sorcerer seen in the game proper.
  • The above story almost repeats in Fire Emblem: Mystery of the Emblem, when Wendell's two pupils, Merric and Arlen almost come to blows with each other due to the latter's jealousy of the former for being given the Excalibur tome. Thankfully, Wendell comes to Arlen and gives him a well-deserved What the Hell, Hero?, even citing that what he's doing is no different from what Gharnef did.
  • In Fire Emblem: Path of Radiance, Greil (when he was known as Gawain, one of the Four Riders of Daein) once trained the Black Knight in swordsmanship. In the Mad King's War, Greil and the Black Knight faced each in a duel in which Greil was slain.
  • In Fire Emblem: Three Houses, any student character who joins the Adrestian Empire during the timeskip becomes this to the Church of Seiros' Officer's Academy. This includes Ashe on Silver Snow and Verdant Wind, Lorenz on all routes other than Verdant Wind, and any Black Eagle you don't recruit on Azure Moon or Verdant Wind (bar Edelgard and Hubert, who were conspiring against the Church to begin with). There's also a case for the Black Eagles and any student you recruit on the Crimson Flower route, where you side with the Empire, but your influence turns the Empire into an Anti-Hero faction instead of an unquestionable villainous one.
• Forever Home: Corporal Slash once took in two street urchins, Barclyss and Heindrovia, to recruit them into the Aurian resistance and to teach them how to harness their innate magical talents. Both started out kind and generous, but Barclyss eventually became a psychopath willing to kill the resistance's POWs, causing him to be expelled. While Heindrovia still retained most of her good qualities, she ended up following Barclyss out of misguided love.
• Ghost of Tsushima has Tomoe, a talented peasant woman who was trained in the Way of the Bow by master archer Sensei Ishikawa, who treated her as though she were his own daughter. Unfortunately, Ishikawa pushed Tomoe too hard due to his perfectionist methods, resulting in her snapping and attacking him before fleeing. When she gets captured by the Mongols, Tomoe offers her services to them and teaches them Ishikawa's Way of the Bow, which they use to terrorize the people of Tsushima, and it's up to Jin Sakai to help Ishikawa stop Tomoe throughout the latter's questline.
• Kingdom Hearts: The first six members of Organisation XIII were pupils to Ansem the Wise, the king of Radiant Gardens who helped him in his research into the Heart. Eventually, they turned on him and turned themselves into Heartless. Only not really. Only Xehanort and Braig apply. The other Apprentices were forcibly turned into Heartless and were manipulated into joining Xemnas under false pretenses upon becoming Nobodies.
• The Naughty Sorceress of Kingdom of Loathing can be found in Fernswarthy's ethics class. He wasn't that nice a guy, but she wasn't that good a student either.
• Legend of Legaia
  • Songi is this to Master Zopu and a Rival Turned Evil to Gala. Zopu and Maya both state that Songi was a good child, but his pride and anger at always being second best to Gala caused his decent unto evil.
  • Kazan's former pupil was the swordsman Rauss. The latter was gradually corrupted by the Ultimate Fang into a Blood Knight, and his desire to fight his former master led him to a Face–Heel Turn ending with the master killing his former pupil.
• The Legend of Zelda:
  • The Legend of Zelda: The Minish Cap: Said by Ezlo about Vaati, who "became enchanted by the wickedness in the hearts of men."
  • The Legend of Zelda: Spirit Tracks: Byrne was an apprentice of Anjean in the Tower of Spirits. He desired power from the good spirits, and when he was not granted it, he left and reached out to serve the Demon King Malladus.
• Metal Gear Solid 2: Sons of Liberty: The demolitions expert Peter Stillman accidentally gives rise to a Mad Bomber, Fatman (real name unknown), a wannabe public enemy who has turned his knowledge toward terrorist bombings. Like any good Star Wars yarn, Stillman is cut down by one of Fatman's booby traps, leaving the callow, blond hero to finish the job.
  Stillman: Microwave. With a 7-foot range. It's not a technique I taught him. Neither was that multi-bomb booby trap. Looks like he's far surpassed me as far as explosives technique goes.
• Mortal Kombat:
  • Frost was a Lin Kuei assassin and cryomancer that Sub-Zero took under his wing, until she decided to try and kill him so she can take control of the Lin Kuei for herself. In Mortal Kombat 11, she turns to evil and joins Sektor and Kronika, voluntarily turning herself into a Cyber Lin Kuei and leading the Tekunin, overseeing the horrific process of turning Lin Kuei into cyborgs. When he sees her again, Sub-Zero is visibly disgusted at what his once-protegee has become.
  • Liu Kang is another character, whom in the alternate timeline originally was a good pupil to Raiden and Earthrealm's champion, until the two split near the end of [1], arguing on how to defeat Shao Kahn, which led to Raiden killing Liu Kang, after which Liu Kang curses Raiden with his dying breaths. He would later return in [2] as a revenant, bound to Shinnok's will, with an immense hatred of the Thunder God, blaming Raiden for his past failures.
• Warcraft III: Uther Lightbringer and Arthas Menethil. Arthas is driven to harsher and eviler tactics to defeat the Undead Scourge over the course of the Human campaign, ultimately taking up the cursed blade Frostmourne and becoming the Death Knight we all know and love and killing Uther during the Undead campaign.
• War of Omens: Listrata dedicates her life to the task of avenging her parents' death. Step 1 of that plan is conquering an island chain (the Phenetik islands) as a thesis. However, her mentor, Ashkar views Listrata as a thug for her treatment of the Phenetikians during her conquest.

Web Animation

• RWBY: Inverted. After the previous leader stepped down, the White Fang changed from a faunus rights organization into a terrorist organization. As one of the leaders, Adam Taurus was in a position to school Blake Belladonna in the new way of doing things. Blake described Adam's descent into extremism as gradual, justifying violence as accidents, then self-defense, then necessity. When the pair take part in a train heist, Adam intends to blow the train; upon asking about the innocent humans on board, Blake is concerned to hear Adam reply "What about them?", finally seeing how far he fell from grace. As a result, she abandons Adam, rescuing the train of people in the process, and goes on the run from the White Fang. She decides to attend to Beacon Academy and train to become a Huntress, someone who protects the people from harm. For betraying him, Adam vows to destroy everything she ever loved, guilt-tripping her into feeling like she's to blame for his actions in destroying Beacon Academy and maiming her teammate, Yang. It eventually leads Blake to vow to take back the White Fang from him and restore it to its former peaceful model.
• Inverted in SuperThings. Enigma was original Professor K.'s young assistant. Once he learned the truth of Clank Corp.'s motives, he quickly abandoned the cause. He eventually would fall into the stead of Colorflash, honing his magic skills further.

Webcomics

• In Our Little Adventure, Thomas Stratus was one of Brian Souballo's old magic teachers back before Brian went all megalomaniacal.
• Weregeek has it Played for Laughs by Dustin and Joel, which is basically them doing the confrontation talk between Kenobi and Vader in A New Hope, but in terms of being a Dungeon Master.

Western Animation

• Zhao from Avatar: The Last Airbender is a former pupil of Jeong-Jeong’s. Once he learned how to Firebend, he then sought to use his abilities to aid his own ambitions. Jeong-Jeong tells Aang that his pupil (who he didn’t name at the time) never learned self-control and his bending becoming more dangerous and untamed.
• Played with in Batman Beyond with Kairi Tanaga and her pupil Zander. Zander was a test-tube baby created by Kobra to be the perfect leader and had thus been effectively brainwashed from birth to follow their teachings and beliefs, while Kairi believed deep down he was not an evil person at heart but simply doing what he'd been taught to do from day one, and that she could save him by teaching him the honorable ways of the Bushido. While he certainly has virtues and is mostly Obliviously Evil, he never-the-less can't be swayed and dives head-first into the role of the evil leader of Kobra, resulting in he and Kairi's deaths.
• Albedo in Ben 10: Alien Force and onward was an apprentice to the Big Good Azmuth, but the two had a falling out over whether Ben was worthy to wield the Omnitrix as Albedo believed Humans Are Stupid. After the two split, he made his own bootleg Omnitrix and accidentally turned himself into Ben's Evil Twin before invading Earth in an effort to undo it.
• Inverted in Carmen Sandiego with the title character, who was raised and taught by the criminal organization V.I.L.E, before stowing away on a mission and discovering their true sinister nature, as well as having a chance encounter with an archeologist who explained to her the meaning that ancient artifacts have to the history of the culture they came from.
• In Dungeons & Dragons (1983), the Dungeon Master revealed that Venger was a former pupil. In the unaired series finale Venger is revealed to be Dungeon Master's son.
• Ewoks. The second season episode ''The First Apprentice" features Zarrak, who was master Logray's first apprentice before he turned to the dark side.
• Felix the Cat (Joe Oriolo): the Master Cylinder was an academy student of the Professor's when a lab explosion caused him to be housed in a tin casing. He proclaims himself to be king of the moon and is not beneath double-crossing the Professor.
• Fukushima from the Kim Possible episode "Exchange" was a student of the Yamanuchi Ninja School. He turned out to betray the school and helped Monkey Fist obtain a powerful weapon. It's not really explored why he did so, either he was already paid by Monkey Fist, or he only turned after Ron came to Japan. He could have felt insulted that Ron received honors that according to him should not be given to "outsiders". Or else he became jealous of Yori's shows of affection for Ron.
• Kuvira of The Legend of Korra was once a promising apprentice of Suyin Bei Fong that she treated as one of her own children and was Captain of the guard of Zaofu. After the fall of the Earth Kingdom due to the events of Book 3, the two had a falling out over whether or not Zaofu should militarily pacify the now-fractured Earth Kingdom. Kuvira eventually took Suyin's elder son, her engineer, the security forces as well as Zaofu's richest residents to form what eventually became the Earth Empire.
• Inverted in Men in Black: The Series where Big Bad Alpha was Kay's mentor until he came across a powerful and illegal alien device that allowed him to assimilate alien body parts.
• Mighty Max: The villian Skullmaster used to be the prized student of the wise Lemurian scholar, Virgil, until Skullmaster turend evil, wiped out Lemuria and tried to conquer the world.
• Morro of Ninjago was once a student of Sensei Wu's, and was the first person that Wu considered might one day be the Green Ninja (this universe's version of The Chosen One). When this turned out not to be true, Morro became enraged and sought to prove destiny wrong, leading him down a darker path which ultimately left him Barred from the Afterlife and trapped in the Cursed Realm as a ghost. Although he serves as the main antagonist of Season 5, he is redeemed in the made-for-TV special Day of the Departed and is allowed to pass on to the true afterlife in peace.
• She-Ra: Princess of Power: Shadow Weaver and Castaspella were both pupils of the wizard Norwyn, but Shadow Weaver became dissatisfied with Norwyn's teachings and jealous that Castaspella was progressing faster than her. She defected to the Horde and cut a deal with Hordak to increase her magical powers.
• Transformers: Animated. While never really elaborated on, Lockdown was once a pupil of Yoketron's. At some point, he abandoned the Cyber-Ninja dojo — only to return, sometime after Prowl joined, to make off with the dojo's protoforms and to kill Yoketron. Oilslick may also apply for this trope, but with the lack on information on his past, it's debatable.

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