Redemption arcs seem to go one of two ways: either the character dies, or the character lives. Sometimes their dying acts are the ones that redeem them – sometimes the only possible thing that can redeem them is death – sometimes they die immediately after having redeemed themselves, just when things have started looking up again. It all depends on how much you want your readers to yell at the book.
It seems to me that a dead-but-redeemed character is – well, not lazy per se. It definitely has an emotional impact on the other characters, and can throw a nice wrench into the plot. But in terms of character development, there’s not much you can do with a dead person unless you reanimate them somehow. Ghosts, zombies, someone from their past ready to rain bloody vengeance on them, a long lost child, et cetera – a little far-fetched, maybe, but you get the gist. It’s still possible to influence how a character is perceived if you have secrets ready to be revealed at a plot-convenient point. Cough, JKR, cough. But even then, what’s mostly happening is the changed perception of a character – Dumbledore can’t exactly react to having his secrets revealed. Oh no, he used to be Very Good Friends with Wizard Hitler back when they were teenagers. That’s … some loaded information right there, but the guy is dead. Harry can’t confront him about it. No one can. Unless you’re doing a prequel (where the dude is alive), it’s essentially an “oh that’s nice, but what does it have to do with the plot?”
Whereas a redeemed character that lives – now that’s where it gets nice and messy.
Because the thing about redemption is that it isn’t a one-and-done deal. You can’t take a villain, or an anti-hero who’s done some messed up things, and then wave a magic wand and say that everything is fine now because he Had a Change Of Heart. Okay, again, that’s nice, but why did he have a change of heart? How did he take that change and use it to affect the world around him? How are the other characters reacting to this change?
You can’t wring your hands and say “oh I’m terrible” and then just keep doing the destructive things you were doing before. Or, you can (and people often do), but it has to have consequences, and also it doesn’t count as redemption.
Roll your eyes all you like, but the best example I can find of a redemption arc is in Avatar: The Last Airbender. Zuko has a few false starts, and they matter to the plot and the other characters. He’s forced to confront his mistakes and how they affected the world around him. He acknowledges what made him the way he was, and he takes responsibility for his actions, and he actively works to heal the damage he’s done. He develops friendships with the people he once considered enemies. He reconciles with his uncle. He overcomes his rotten family – confronts their toxic behavior – and at the end of the series, he’s grown as a character and become an actual good guy. Yes, it’s a kids’ show that aired on Nickelodeon, but it goes over some really important themes, and it shows that goodness and kindness are things that you do, and traits that you can practice. The show never took it easy on Zuko. He wasn’t handed redemption on a silver platter. He had to work for it, and it made his characterization a hell of a lot stronger.
It’s easy to die for a cause. It’s harder to live for one.