History Main / APupilOfMineUntilHeTurnedToEvil

** 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 ''[[VideoGame/MortalKombat9]]'', arguing on how to defeat Shao Kahn, which led to [[AccidentalMurder Raiden killing Liu Kang]], after which [[DyingDeclarationOfHate Liu Kang curses Raiden with his dying breaths]]. He would later return in ''[[VideoGame/MortalKombatX]]'' as a revenant, bound to Shinnok's will, with an immense hatred of the Thunder God, blaming Raiden for [[MyGreatestFailure his past failures]].

* ''ComicBook/{{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 HeelFaceTurn, though his relationship with the rest of the family is still strained and he's still prone to lethal force when sufficiently pushed.

* In ''Manga/DemonSlayerKimetsuNoYaiba'', 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 [[BigBad 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 [[DrivenToSuicide committed seppuku]], much to Zenitsu's fury and despair.

* ''Franchise/MortalKombat'' has Frost, 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 ''VideoGame/MortalKombat11'', 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 [[UnwillingRoboticization turning Lin Kuei into cyborgs]]. When he sees her again, Sub-Zero is visibly disgusted at what his once-protegee has become.

* Vargas, in ''VideoGame/FinalFantasyVI'', [[SelfMadeOrphan kills his father]] and master ([[spoiler:though said master turns out to be alive after the TimeSkip]]) out of the belief that he favored Sabin.

* ''Manga/{{Naruto}}''

* Inverted in ''[[Film/BillAndTed Bill And Ted's Bogus Journey]]'', where it is Rufus's old teacher (even if for gym), [[SignificantAnagram De Nomolos]], who turns to evil.

* In ''Manga/DemonSlayerKimetsuNoYaiba'', 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 [[BigBad 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 [[DrivenToSuicide committed seppuku]], much to Zenitsu's fury and despair.

* In ''Manga/DemonSlayeKimetsuNoYaiba'', Kaigaku was the student of the former Thunder Hashira, alongside Zenitsu Atsaguma. Known for his jealousy, cowardice, and cruelty, he frequently berated Zenitsu, who saw him as a brother figure. He eventually became a demon, and became the Upper Rank 6 of the 12 Kizuki, following the death of the former holder.

* ''Manga/RurouniKenshin'': The trope title is almost a word-for-word utterance by [[{{Ninja}} Old Man Okina]] after fully realizing that his most beloved disciple, Aoshi, has fallen entirely to the dark side -- and is in league with [[BigBad Makoto Shishio]], to boot. Specifically, he ask Kenshin to put an end to Aoshi's life. However, in a moment that also defies BrokenPedestal 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, [[DefiedTrope Aoshi realizes the errors of his way.]]

* In ''Manga/SoulEater'', Asura was Shinigami's apprentice [[spoiler:and as it turns out, son]] until he went insane and threatened to destroy the world, and had to be sealed away.

* Vargas. in ''VideoGame/FinalFantasyVI'', [[SelfMadeOrphan kills his father]] and master ([[spoiler:though said master turns out to be alive after the TimeSkip]]) out of the belief that he favored Sabin.