Willow: Dark Willow is unleashed and kills her friends one by one in a fit of rage including Tara. We've seen Willow's fear progress from stage fright into sucking at magic into being ashamed of who she was in high school, but by the end of the show she's definitely afraid of letting her bad side out again.
Yeah, I think you're right. This is what the First used to freak Willow out in the first place. 'You'll lose control and everybody will die so why not just stop so you can be with Tara forever...' etc.
Buffy: The slayer part of her taking over/becoming stronger. Her inability to 'feel' or connect to her friends/family. Her life being one, never-ending slaughter of oogley demon-things.
Giles: See 'Something Blue'.
😛
But seriously, Giles' fears usually revolve around Buffy. I don't think its something like 'not being needed' (he's had that twice already- in S4 and S8) but more 'I have the information that can help her and for whatever reason she won't let me.' That type of thing. Being unable to save her because of mistakes he has made.
Dawn: People forgetting that she ever existed at all. She can see them but they don't see her. They just head on with their lives and seem
happier without her there.
Faith: Take Wesley's speech to her in 'Release' (you're sick, you've always been sick', etc), but have
Buffy say it and then have Buffy (and maybe everyone else that Faith has ever wronged) chase her around Sunnydale with a big ol' knife.
Also having Angel sneer and say that he should've killed her way back when.
Fred: She never left Pylea. She keeps having flashes of herself still back in that cave, but instead of writing out calculations she's snapped and is now drawing pictures of her imaginary rescuers...
