I'm kind of a fan of the redemptive character arc. I kind of alluded to that in one of my character archetype from so long ago. I don't imagine that's unique to me, just based on the popularity of redemptive arcs. I think a lot of people tend to empathize with characters that have made mistakes, and are trying to correct them, or atone for them.
Of course, there would seem to be limitations to the arc. How long can you keep a character motivated to act based on that need for redemption. I suppose for quite some time, since Spider-Man is a kind of redemptive character, depending on how you view his actions following Uncle Ben's death*. It probably varies by the creator, and what the character's done that requires redemption. For example, in season 4 of Angel, when Faith tries to sacrifice herself to get Angel back, with the idea that would be enough to make up for her past misdeeds, Angel tells her they never stop paying, that essentially, one has to keep working for redemption** (that's how I recall it going, anyway).
The other common end for a redemptive arc seems to be when it falls apart. I'd say Sandman (Marvel version) and Juggernaut would be two examples. For the Juggernaut, his redemption ceased when he decided there were things more important to him than fighting the good fight, namely, being as powerful as he used to be. For Sandman, his best efforts just didn't seem to bear fruit, and I think he just gave up hope after awhile. I know something happened that caused his Avengers stint to end disastrously, and things deteriorated from there.
There are two endings I don't think I see as much though, which is why I thought I'd ask you about them. First, the character actually feels redeemed. As readers, we might reach this point long before the writers decide it has happened. I'd think you could say a character reached this point when people actually start to think of them as a "good guy", because I think that would imply they've been at it long enough that we, as the audience, have accepted them as doing good for genuine reasons. We don't see them as a killer that happened to help out the heroes a few times, they are one of the heroes. It seems rare that the character, in their own mind, feels they've moved beyond that stage. Most of the time, I think it occurs in such a way that the character decides they'll continue to help others because they enjoy it, or they think it's the right thing to do, rather than to attempt to balance a spiritual ledger. The other option, I suppose, would be for the character to reach the stage where they feel they've been redeemed, and call it a day. They've done enough to make up for mistakes of the past, and now they'll be leaving, thank you very much. I'd imagine that might get more use in a creator-owned, finite story, rather than a serial one, simply because in an ongoing story, you can't necessarily have characters (especially the protagonist) deciding they're done and they're leaving the business, because it kind of hurts the story. I can't think of any examples offhand.
The other one is the redemptive arc that gets cut short due to death. This is the one that started this with me, while I was watching Trigun. Late in the series, the episode after this disagreement in fact, Nicholas D. Wolfwood ends up fighting the man who taught him, a fellow named Chapel. Wolfwood was supposed to kill Vash, after having been told to ensure his safety for quite awhile, and having grown to consider Vash a friend, refused to do so. Wolfwood manages to triumph over Chapel, wounding him, and is left with a question: Kill Chapel or not? Up to this point, Wolfwood had shown no qualms about killing, and has only refrained from doing so when Vash actively tells him not to beforehand. Here, he decides to follow Vash's example, and lowers his gun, albeit with some difficulty***. He tells Chapel that he'll still use what he was taught, just in a different way, takes Chapel's apple, and walks away. Then Legato takes control of Chapel, and Chapel shoots Wolfwood, wounding him mortally. Wolfwood has time to tell Vash where to find Knives, and then walk into a church, where he thinks about reincarnation, but also about all the things he could do to help people like Vash does. Then he dies. Cue much crying by various other characters.
It strikes me as somewhat strange, that at the moment the character has this change of heart, renounces his killing ways, and decides, as he put it, that 'there are plenty of ways to save everyone', his story ends. This is not some cold-blooded, heartless killer. This is priest, who also happens to be a gun-for-hire, because it pays the bills that keep the orphanage he established running. He is, in my estimation, solidly in the grey area between good and evil. Yet his new view on things never really gets a chance to produce any results****.
It happens because he's just a supporting character, and his death serves a purpose in the main character's own arc, forcing him to question whether never killing your enemies is actually wise. After all, Wolfwood had done just fine doing things his way, and the first time he tries Vash's method on his own, he dies, so is Vash's way as correct as he's maintained? I can't think of too many similar situations, where the character barely begins their new path before they get taken off the board. I was considering Spoiler in War Games, since it came about ostensibly because she wanted to prove Batman wrong about her, but I don't think that story involves Spoiler changing something, or trying to atone for something. She was trying to prove herself, and she'd been doing that ever since she first appeared. I'd think examples of this would have to be supporting characters, since it's easier to kill them, but I could see someone doing a movie or limited series of some kind where the main character falls short in their attempt to change their ways.
So, you have any ideas?
* I think some writers portray the death as a lesson Peter learned, and it serves as a reminder of the man Ben was, which leads to Peter trying to honor him. Other writers argue that all the superheroics are a guilt complex, a need to make up for not saving Ben by stopping the criminal.
** Which, I must say, is not a particularly great pep talk if you're trying to keep someone from going into the light. "Hey guess what, no matter what you do, you'll always need to do more, it'll never end. Now get up and continue the endless struggle!"
*** He's holding the gun with his right hand, and actually raises his left hand and uses it to lower the barrel, as though he's fighting with himself.
**** And it works out badly for everyone. it gives Vash something else to feel guilty about, and makes Chapel feel he owes Wolfwood a debt of honor. So he tries to kill Legato, and not only does he fail, Knives traps him in a place described as somewhere between existence and death. Sounds like he would have been better off if Nicholas D. had just killed him.