Aww, poor Willow. All the hate! I love her. S7, she kind of bugs me, and I've already explained why so many times...
Honestly, other than Spike, who I feel Joss ruined like he does so many amazing characters, Buffy. She starts out as fun and rebellious, and slaying was just a part of her. By the end, all she is is the Slayer. It's her whole identity.
Season 6 really disappointed me. She lies to her friends, degrades herself, even tries to kill them because a world in which she's crazy seems better to her than the world in which she actually lives. She's not even a thread of the tapestry she once was.