Love Redeems is a TV Tropes term used to describe when a villain or jerk turns good after falling in love. While this Trope also works by love for a family member like a brother or son, this wiki will only mention villains redeeming themselves because they fell into romantic love.
YuYu Hakusho: Yusuke's ancestor, Lord Raizen was a flesh eating demon fell in love with a human nurse who stood up to him and changed his ways. He refused to eat human flesh again and as a result, was dying over centuries by the time Yusuke meets him. Yusuke succeeds him after his death.
Sailor Moon: Nephrite, in the anime, fell in love with Naru (Molly in the English dub). Because of this, he turned his back to the Negaverse and sacrificed himself to save Naru.
Care Bears 2: A New Generation: The main villain of the film, Dark Heart, an entity of pure evil, turns not only good, but human as well when he falls in love with a human girl who dies at the end. After admitting he cares, his powers leave him and the girl is brought back to life.
Harry Potter franchise: Snape left the Death Eaters and turned spy for Dumbledore after Voldemort killed Lilly, Harry's mother and the only woman Snape truly loved.
Avatar: The Last Airbender: Mai turns on Azula to save Prince Zuko and admits she loves Zuko more than she fears Azula. Her betrayal, along with Ty Lee's, ultimately help in driving Azula insane with paranoia which helps Zuko and Katara defeat her.
Gargoyles: Xanatos goes from villain of the show to one of the Gargoyle's greatest allies after he falls in love with Fox and the Gargoyles save their son.
Megamind: Megamind, a supervillain, begins to date Roxanne Ritchi (under the disguise as a man named Bernard) and as a result, has less time for his evil. At the end of the film, he completely reforms and begins to date her.