Batman issue #127 showed an alternative origin if Batman's parents didn't get killed. In this version, Batman was a criminal called the Blue Bat, and the costume was worn by someone else. This all changed with an encounter with Bruce Wayne, who defeated the crook, took the costume for himself, and became Batman, noting, "This costume that was once a symbol of crime will now become a symbol of justice!"
Detective Harvey Bullock, a member of Batman's supporting cast, was introduced as a corrupt cop, but he saw the error of his ways. Since then, he's been working hard at cleaning up both Gotham City and his reputation.
Another Batman-related example: Scientist Kirk Langstrom, alias the supervillain Man-Bat, is often portrayed as trying to make up for the damage his Superpowered Evil Side has caused.
In Batman: White Knight, The Joker is cured of his insanity and transforms into Jack Napier. As a result, he wants to make up for his past as the Clown Prince of Crime by becoming Gotham's White Knight.
Pre-Flashpoint Arsenal in Convergence: Titans is making a better attempt to atone for his actions after he was maimed by Prometheus and his daughter Lian died.
Pre-Zero Hour: Crisis in Time! Hal Jordan is this as well. Getting depowered by the dome brought Hal back to his senses and he's legitimately regretful for what he did as Parallax. Unfortunately, the minute the dome comes down and his abilities come back he goes nuts once again.
The Vampire Batman in Convergence: Swamp Thing seeks redemption by teaming up with Swamp Thing in ridding the vampires from his Gotham City. After eliminating the queen vampire and thereby turning every vampire back to being human (except for Vampire Batman), Batman allows himself to die under sunlight.
Superwoman of the Crime Syndicate has taken her time on death row to reflect on how she's spent her life, and realizes that both herself and the rest of the Syndicate wasted their lives in the pursuit of crime. She fights the Wonder Woman of Justice Legion Alpha for the sake of saving the Metropolis of her world in an attempt to fully atone for her actions and be the hero she now understands she could have been.
Crisis on Infinite Earths: Pariah, whose attempt to explore the origin of the universe has resulted in the destruction of his parallel universe, and personally believes that he may also be responsible for the destruction of the other parallel universes until the Anti-Monitor reveals that he himself is personally responsible for the latter.
Green Lantern: Post-Parallax Hal Jordan. Although Green Lantern: Rebirth revealed he was being influenced by the evil entity Parallax when he destroyed the GL Corps, he still feels responsible for his actions when being possessed, just like Kyle when he was possessed during the Sinestro Corps War. Part of his interaction with the Corps is trying to rebuild the trust he lost when he killed his fellow Corps members and essentially destroyed the original Green Lantern Corps.
Hamilton: Yes! Thank you! I've worked so hard, thrown everything away, committed terrible crimes... Take me away! I'll gladly accept my punishment knowing Luthor's true nature has been exposed.
In Bizarrogirl, the Girl of Steel and Bizarrogirl work together to save the latter's homeworld. As teaming up, Bizarrogirl learns morality in human terms, the difference between saving people and killing them and realizes back on Earth she killed a man because he was too loud. Bizarrogirl decides to punish herself and asks Supergirl (who is struggling with her own feelings of guilt) if she'll even be able to find some sort of redemption:
Bizarrogirl: Does self-punishment end, Supergirl? Supergirl: It might never end, Bizarrogirl. We can be sorry for what we've done, be sorry for hurting others, but it's what we do afterwards that really matters.
The Krypton Chronicles: When Superman and his cousin travel to Rokyn, they learn that several reformed criminals -including some few of their former enemies like Brenn-Bir and Shyla Kor-Onn- are helping in the rebuilding of Kandor to atone for their misdeeds.
In The Supergirl Saga, Pocket Universe Lex Luthor becomes this when he accidentally let loose the Phantom Zone criminals from their imprisonment for them to start their reign of terror and devastation on the Earth, even to the point of instantly annihilating five billion people on the planet via Atmosphere Abuse. At the end of the story, when Lex Luthor is killed along with the remaining members of his resistance force, he says to the mainstream DC Universe Superman that he knew about the Gold and Green Kryptonite samples hidden in Superboy's lab, but he refused to use them because he wanted the Phantom Zone criminals' defeat to be by his own hand, and now regrets that decision and has Superman promise to never let that happen again.
In a Silver Age story, "The Secret of Kryptonite," a scientist named Mal Evans accidentally made Superman's vulnerability to the mineral public knowledge when Clark was a boy. As a result, Evans fled and changed his identity in shame and in fear of Superman's reprisal to work as a humanitarian. Superman would find him years later and reassure Evans that he knew it was an accident and he was forgiven long ago.
Wonder Woman (1942): Paula didn't really want to work for the Nazis in the first place, but to save her daughter threw herself into the work and committed many horrific acts and ruined and ended many lives. Once her daughter was safe she spent the rest of her life doing everything she could to take down the Nazis and their allies and help people whenever she became aware of an opportunity to do so.
In Wonder Woman: The True Amazon, Diana becomes Wonder Woman as penance for her crime in unleashing monsters to win the Contest, and is also tasked with re-sealing the monsters away.
