I think these meet your criterion of starting solely with anti-good characters:
Cecil from FF4 starts as a literal dark knight before realizing he’s working for an evil empire, becoming a paladin, and saving the world.
John Preston from Equilibrium (the protagonist, played by Christian Bale) is a fascist secret police agent until he accidentally feels emotion, then realizes that anti-emotion fascism is bad and overthrows it.
Megamind from Megamind is a supervillain who realizes that actually he should be a hero. (Maybe this shouldn’t count because there’s initially a superhero? But the protagonist is Megamind throughout.)
Grace from Infinity Train season 3 starts as a cult leader trying to maximize the in-universe utility function (literally!), but got the sign wrong so she’s absolutely terrible. But she meets a small child and realizes she’s terrible and works to overcome that.
Gru from Despicable Me starts out a supervillain but eventually becomes a loving father and member of the “Anti-Villain League”.
Joel from The Last of Us is a murderer in the post-apocalypse who is redeemed by finding a surrogate daughter figure and at the end of the story… I have been advised this is not a suitable role-model for an AI, please disregard.
Some themes of such redemption stories (safety implications left to the reader):
Adopting one or more children (1, 4, 5, 6)
Having an even eviler version of yourself to oppose (2, 3, 4, 5)
I think these meet your criterion of starting solely with anti-good characters:
Cecil from FF4 starts as a literal dark knight before realizing he’s working for an evil empire, becoming a paladin, and saving the world.
John Preston from Equilibrium (the protagonist, played by Christian Bale) is a fascist secret police agent until he accidentally feels emotion, then realizes that anti-emotion fascism is bad and overthrows it.
Megamind from Megamind is a supervillain who realizes that actually he should be a hero. (Maybe this shouldn’t count because there’s initially a superhero? But the protagonist is Megamind throughout.)
Grace from Infinity Train season 3 starts as a cult leader trying to maximize the in-universe utility function (literally!), but got the sign wrong so she’s absolutely terrible. But she meets a small child and realizes she’s terrible and works to overcome that.
Gru from Despicable Me starts out a supervillain but eventually becomes a loving father and member of the “Anti-Villain League”.
Joel from The Last of Usis a murderer in the post-apocalypse who is redeemed by finding a surrogate daughter figure and at the end of the story…I have been advised this is not a suitable role-model for an AI, please disregard.Some themes of such redemption stories (safety implications left to the reader):
Adopting one or more children (1, 4, 5, 6)
Having an even eviler version of yourself to oppose (2, 3, 4, 5)