It's sort of a Sequel-itis. Author completes one idea, but the story must continue...attempt to do it again because they have no new ideas. Do the old one again, but bigger and badder.

Exactly. Or smaller and with robots, as the case may be. :)

I'm not sure I agree that there are lines that can never be crossed. But if they're crossed, the story must acknowledge that and work hard at uncrossing them - and that uncrossing can't just be about the guilty party feeling guilty, because ultimately that doesn't make anything better at all. The problem with some redemption stories is that, to me, they often come across as supremely selfish. "All those people I hurt are an opportunity for me to learn something about myself, now behold as I brood a while before repeating the exact same mistakes." Fuck that.

Angel the show, ultimately, tried a little too often to have it both ways. I think I like that series more than some, but there's no denying that there's a pretty profound gap between the show it presents itself as (The Dark Avenger And Protector Of Little Ladies) and the philosophical questions it claims to address ("If nothing we do matters" etc, not to mention Angel's own inherent Angelusness).

...Actually, that's probably another upcoming meta post.