In Ratatouille, Anton Ego rediscovers his love of food after tasting Remy's cooking, and goes from vindictive food critic to Alfredo and Remy's financial backer.
Dr. Tenma in the 2009 Astro Boy film. Tenma spends the first two-thirds of the movie acting like a king ass, blatantly telling Astro he doesn't want him and kicking him out, and later helping the crazy politician that wants to kill him. Tenma then has a change of heart, risking his own life and freedom to save his 'son'.
Iago from Disney's Aladdin spent the entirety of the first film on Jafar's side. The beginning of the second film, Aladdin: The Return of Jafar, sees Iago escape from Jafar's lamp and slowly turn face over the course of the movie, even offing Jafar for good by kicking his lamp into magma. Not that Iago's all that heroic, but his conscience does get the better of him on a number of occasions. He grumbles over it a lot.
There are some male turns in the series. There was the Muchtar, and Aladdin's old friend-turned-monster Amal.
Like Iago, Cinderella has a character who starts off rotten to the core in the original movie, and then turns in the sequel, this being Anastasia. The first sequel, Cinderella II Dreams Come True, has her as one of the protagonists in "An Uncommon Romance", where Cinderella helps her win the heart of a baker she falls in love with. But the third movie, Cinderella III: A Twist in Time, has her start things off by stealing the Fairy Godmother's magic wand and handing it to her mother. From that point on, she poses as the one who the prince fell in love with...and her conscience slowly gets the better of her as she realizes what love really means until, at the end of the film, she can no longer go along with Lady Tremaine's plan, and openly defies her. As such, she's the only one of the three Tremaines whose story ends with a happily ever after.