At no surprise, Faith - She definitely went awol for a bit too long, but to paraquote Buffy and Giles (I can't find the actual quote): "Are you going to give up on her?" "Never" "Then she might stand a chance". Even I know that even completely messed up people can still do good... they just need a bit of faith. (Hahahaha)
Dawn, to an extent - I think she was just going through a lot, through a very short time. You try finding out that you never existed and not only your own life, but the lives of everyone you know, were all fabricated lies.
Xander - I can't recall him doing anything particularly questionable, but I can empathise with how he usually feels in the Scooby Gang. I'm sure I'd stand by him.
Leo, from the book series - I'm unsure how much I can write about Leo before it gains spoiler status, but I can say he always acted with fair intentions, and never means to hurt anybody. And on that subject...
Oz! Sure, he's a werewolf, but you can't hold that against him. I'm not sure anyone in the series who actually met Oz disliked him, and you've gotta love how existential he is all the time.
And, of course, Buffy - She died twice, and still isn't done with life. I think she's earned the right to make a few mistakes. In fact, here's a quote I can find: "I tried to kill my friends, my sister, last week and guess how much they hate me now? Zero. Zero much."
