Villains' Absolution

"And what happened then? Well, in Whoville, they say, that the Grinch's small heart grew three sizes that day."

- The Narrator on the Grinch's redemption.

Villains' Absolution is the trope/phenomenon describing that some villains give up their evil ways to become good.

This event is essentially a form Heel-Face Turn scenario where a villain decided to become a good guy, though in Villains' Absolution's case, the villain would reflect the error in their ways and sees that in spite of how far he/she go in the path of evil, he/she realized that he/she still have the chance to return to the good side.

Cartoons, Manga and Anime

 * Sunset Shimmer: After Twilight Sparkle and her human world friends used the elements in them to defeat Sunset Shimmer, changed back from a demon into normal, she immediantly shed tears and apologizes for her actions.
 * Chirn: As soon Chirin invaded his childhood farm, he saw a lamb that was like him when he was young and his mother saving him. He then had some second thoughts, but the wolf did had the same beliefs, so Chirin stopped him, saving the sheep for he remembered he's the wolf who killed his mother.
 * Terra: After the Teen Titans return, Slade abused her and therefore went against him.
 * Dark Heart: When Dark Heart was attacking the Care Bears, he hit Christy as well, and he started to feel remorse since she save him from drowning.
 * The Grinch: His in How the Grinch Stole Christmas is no doubt one of the most famous absolution in history. After the Whos in Who-Ville sang without the presents, he began to realize that Christmas isn't about presents.
 * And in The Grinch Grinches the Cat in the Hat, the Cat in the Hat along with the other troubled people reminds the Grinch about his mother, and then starts feeling remorseful.
 * Prince Zuko: After some time in the fire palace, Zuko realizes that he should join the Avatar.
 * Mai and Ty Lee: Mai went against Azula for the love of Zuko and Ty Lee went against Azula for Mai.
 * Nightmare Moon: Twilight Sparkle and her friends used the Elements of Harmony to transform Nightmare Moon back into Princess Luna
 * Discord: Because Fluttershy called Discord her friend for making her house lively, Discord felt good. But then started to abuse it for his advantage, but then Fluttershy started to snap, but Discord didn't care for he's the spirit of chaos. But then he realizes that he'll lose the only friend he ever made, so he made everything back to normal.
 * Starlight Glimmer: Twilight Sparkle brought Starlight Glimmer into the terrible future after another failed attempt to restore the past, but Starlight was persuasive for cutie marks costed Starlight her only friendship. So Twilight offered Starlight her friendship.
 * Jinx: Kid Flash charmed her saying, she does not have to be the bad guy.
 * Kraehe: Kraehe took a glimpse of her past and discovers who she really is: not the daughter of the Raven, but an ordinary girl. With that she lost her Kraehe side and permanently stayed as Rue for good.
 * Lord Business: Finn tells Business that people's creativeness are wonderful, he's one of the greatest people who ever lived and he does not have to be the bad guy.
 * Iago: In The Return of Jafar, Iago got fed up with Jafar's abuse and joins the good guys for his own gain, and eventually stars to actually warm up to them, and eventuaully redeems himself by kicking Jafar's black lamp into molten lava, destroying him forever.
 * Carface: In An All Dogs Christmas Carol, after the visits of Charlie, Itchy and Sasha, Carface sees the errors of his ways and decides to stop Belladonna
 * Scalawag and Igor: After Pinocchio saves Scalawag and Igor from the Pike, they start to have second thoughts about selling him to Puppetino and the Emperor of the Night.

Live-Action Movies

 * Darth Vader: His' no doubt one of the most famous absolutions in history. When his son, Luke Skywalker was being tortured by Emperor Palpatine, Darth Vader sacrificed himself to save Luke by throwing Palpatine into the pit. As he was dying, Vader asked Luke to remove his mask so he can see his face for the first and the last time.

Literature

 * Ebenezer Scrooge: His' no doubt one of the most famous absolutions in history. After the visits from the first two spirits and seen what the Ghost of Christmas Yet to Come shown what will his future be like, Scrooge apologizes for all the wrong he did and he will change and honor Christmas in his heart for the rest of his life.
 * The Once-Ler: The Once-Ler realizes the errors of his ways (a little too late) when he chops down the last Traffula Tree of them all

Quotes
"[crying] I-I'm sorry. I'm so sorry. I didn't know there was another way."

- Sunset Shimmer apologizing to everyone for what she done

"Oh. Oh. Well played, Fluttershy. Well played."

- Discord after realizing he'll lose the only friend he ever made if he doesn't turn everything back to normal.

"Twilight Sparkle: Starlight, you're right! I don't know what you went through! But I do know you can't do this! I've seen where this leads, and so have you! Starlight Glimmer: I only saw what you showed me! Who knows what'll really happen? Twilight Sparkle: I've seen it a dozen times! Things don't turn out well in Equestria without my friends! Starlight Glimmer: Ugh! What's so special about your friends?! How can a group of ponies that are so different be so important?! Twilight Sparkle: The differences between me and my friends are the very things that make our friendship strong! Starlight Glimmer: I thought Sunburst and I were the same. But we turned out different, and it tore our friendship apart! Twilight Sparkle: So try again! Make new friends! And if something that you can't control happens that changes things, work through it together! That's what friendship is! And it's not just my friendships that are important to Equestria! Everypony's are! When yours ended, it led us here. But just imagine all the others that are out there waiting for you if you just give them a chance! Starlight Glimmer: How do I know they won't all end the same way? Twilight Sparkle: I guess it's up to you to make sure they don't."

- Twilight Sparkle reasoning Starlight Glimmer to leave the past as it is.

"Darth Vader: Luke... help me take this mask off. Luke: But you'll die. Darth Vader: Nothing... can stop that now. Just for once... let me... look on you with my *own* eyes. [Luke takes off Darth Vader's mask one piece at a time. Underneath, Luke sees the face of a pale, scarred, bald-headed, old man - his father, Anakin. Anakin sadly looks at Luke but then gives a tired smile] Anakin: Now... go, my son. Leave me. Luke: No. You're coming with me. I'll not leave you here, I've got to save you. Anakin: You already... have, Luke. You were right. You were right about me. Tell your sister... you were right. [Anakin smiles and his eyes begin to droop slumps down in death while giving one last dying breath] Luke: Father... I won't leave you."

- Darth Vader's words

"No, Spirit! Oh no, no! Spirit! Hear me. I am not the man I was. I will not be the man I must have been but for this intercourse. Why show me this, if I am past all hope? Good Spirit, Your nature intercedes for me, and pities me. Assure me that I yet may change these shadows you have shown me, by an altered life. I will honour Christmas in my heart, and try to keep it all the year. I will live in the Past, the Present, and the Future. The Spirits of all Three shall strive within me. I will not shut out the lessons that they teach. Oh, tell me I may sponge away the writing on this stone!"

- Ebenezer Scrooge repenting to the Ghost of Christmas Yet to Come, telling he can change and honor Christmas in his heart.

"That there, that's me? Then I... after all this. I'm not the Raven's daughter. I had a mother. I had a father. I'm a normal human being?"

- Kraehe discovering the truth that she is not the Raven's daughter and changes into Rue for good

"You don't have to be the bad guy. You are the most talented, most interesting, and most extraordinary person in the universe. And you are capable of amazing things. Because you are the Special. And so am I. And so is everyone. The prophecy is made up, but it's also true. It's about all of us. Right now, it's about you. And you... still... can change everything."

- Emmet reasoning with Lord Business

"Hey Jafar, SHUT UP!"

- Iago to Jafar while rescuing Aladdin by destroying Jafar's lamp