Aladdin: Iago spends 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.
Bear, and the other members of the Christmas Squad, have a change of heart after seeing Angela save Bobby's life, and help the kids bring back Christmas.
Two of the three unnamed bullies end up helping Angela, Bobby and Marian bring Christmas back.
Kovet himself, due to Angela's angel powers, becomes a nice guy at the end of the story.
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".
Rourke: Aw, you can't be serious. Audrey: This is wrong and you know it! Rourke: We're this close to our biggest payday ever and you pick now of all times to grow a conscience?! Vinny: We've done a lot of things we're not proud of — robbing graves, plundering tombs, double-parking... but, nobody got hurt! Well... maybe somebody got hurt but, nobody we knew.
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. Cinderella ultimately forgives Anastasia and lets her stay in the palace. 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 HeelFace 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 HeelFace Turn hasn't really crossed her mind (rather than rejecting the chance).
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 favor and now Vidia is not only a Sixth Ranger, but also The Lancer of the group.
Mirage in The Incredibles stops supporting Syndrome because he Would Hurt a Child and he calls Mr. Incredible's bluff to crush her, despite his following claims that he was doing so since he knew Mr. Incredible would never kill a person. Regardless, she leaves him (making him shocked and confused) and instead aids the heroes in their escape from Nomanisan Island.
Koati: Jithu starts out fully aligned with the main villain Zaina, and agrees to hunt down Nachi to prevent him from learning new information and undermining Zaina's authority. By the end, he helps push down a pillar to prevent lava from entering the Mouth that Does Not Speak, where the animals are taking refuge.
In Lilo & Stitch: The Series, almost each episode focuses on Lilo and Stitch's attempts to rehabilitate one of the other 625 escaped experiments. Captain Gantu and Experiment 625 has one in the Grand Finalefilm.
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.
The first movie has Sunset Shimmer, whose quest for power is defeated by Twilight and her human friends. After the battle, Sunset accepts Twilight's hand in friendship, and reconciles with the humans. She later becomes one of the main protagonists in the Equestria Girls franchise.
My Little Pony: A New Generation: Phyllis is the initial representative of racist earth ponies, but she has a change of heart after seeing the destruction Sprout wreaks in the name of those values, even putting herself in front of Sprout and his war machine in a desperate attempt to stop his son's madness. Together with the other two leader figures of the pony tribes, she eventually accepts Sunny's message of choosing friendship and unity over fear and division, an act which finally activates the three pony crystals and brings magic back to Equestria.
Pleasant Goat and Big Big Wolf: The Bitter Gourd King, in the third movie, is transformed out of his evil state after his battle with the goats and wolves. For that matter, everyBig Bad and his henchmen in the movies ultimately switch to the good guys' side.
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.
Santa Claus Is Comin' to Town: Winter Warlock changes from bad to good after Kris gives him a present. The entire song "Put One Foot In Front of the Other" is about how changing from bad to good is as easy as taking your first step.
Shrek 2: After seeing how much Fiona hates Prince Charming and only has eyes for Shrek, King Harold feels guilty for not taking his daughter's feelings into consideration and decides to go back on his promise to the Fairy Godmother.
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.
Subverted definitely with Lotso. Played straight with the rest of the Sunnyside toys.
Up: The credits show all of the villain's dogs, including Alpha, assisting the infirm.
Wreck-It Ralph: Ralph attempts to pull this off. The entire idea of "Face" and "Heel" and what it really means to be either is examined and played around with during the story.
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.