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.
Unfortunately, this wasn't the case in Kingdom Hearts: Birth by Sleep whereas Anastasia lets her hatred of Cinderella after fitting the glass slippers turn into an Unversed and get killedmessily, this time being remembered as an irredeemable monster through and through. This is unlike Iago above, who kept his Heel–Face Turn in the game eventually. Then again, the events of the game happened during the first movie's events and she was not given the chance to feel what love really means, meaning the idea of Heel–Face Turn hasn't really crossed her mind (rather than rejecting the chance).
Maximus from Tangled. Starts off as a horse that is too persistent and smart to capture Flynn Rider and bring him to justice. After being forced to stick together by Rapunzel, he started to grudgingly befriend Flynn, and when Flynn was in trouble by his superior and Rapunzel might be in danger, Maximus betrays his human superiors by calling forth the ruffians he helped arrest before to save Flynn and eventually take him to Rapunzel for the climax.
Done by Mr. Pickles and Mr. Trout in The Boxtrolls. Averted with Snatcher and Mr. Gristle.
In Disney FairiesGreat Fairy Rescue, Vidia turns good after leading Silvermist, Rosetta, Fawn, Iridessa, Clank and Bobble to rescue Tinker Bell from humans, and even risks her life to save Tinker Bell from being taken to a a museum to be pinned to a display case. Tink returns the favour and now Vidia is not only a Sixth Ranger, but also The Lancer of the group.
Gideon from Zootopia, though not onscreen. He was a pretty vicious bully as a kid, and was the reason why Judy developed some prejudice against foxes. However when Judy meets him again as an adult, he had grown into a much kinder person, and he apologizes to her for how he used to be.
Moana has a version of this with shades of Good All Along when Moana and Maui realize that the monster they have to defeat to save Te Fiti is Te Fiti, and once she receives the stone back, she immediately becomes a gentle goddess again.