So he tried to “rape” Buffy. Now, even at my most feminist instinct alert, I really wouldn’t go far as to say rape. Because the thing is, she did things that are just as bad to him :

1) He understood her when nobody had a clue, became a true friend and was happy to see her happy- see her smile in return. Yet when she realized she had feelings for him (sexual and otherwise), she treated him like dirt, refused to talk to like normal people after they kissed (which she started.)
2) Basically, despite her insults and rejections (she would not look at him one night and yet would jump to his bones the next..),he let her take all her anger and depression out of him and he just let her-although he could fight back.
3) He never laid a hand on her before she jumped him
4) And she did use him and his feelings for her, just to get over anything that was wrong in her life- including the time her ex came to town with a wife.

So- then she decided she shouldn’t sleep with him at all and dumped him,right? Then when he went over to say sorry about sleeping with another girl- she was actually pissed because he slept with her friend. He said he just wanted to get over her and was willing to do anything for that. Then she was saying she would never trust him, hence she could never love him. O.K.- SO after this unproductive conversation, he kinda lost it. He just wanted to touch her and prove to her that she felt for him.The thing is- whenever he did it before, sooner or later, she let him and just enjoyed it. This time she said no but then she always said no even when she started things. I think he is not all to blame here. Remember, evil, vampire? Supposedly anyway. Of course he went a little far, she despised him for it.
He then left town. I thought he was going to do something to kill her or something. Instead, he risked his life and fought to death to get his soul. She had kept saying he was evil and soulless. And he did. For a while, he nearly went insane: trying to get rid of the images of everyone he had harmed. Then…she saw him, suffering- because of the soul.
So now she was helping him and taking him out of a bad place. He never tried to ask her to take him back. But she was not a bitch to him either. This time, their relationship wasn’t physical. It was much more on a emotional level and she trusted him, respected him. Because in addition to being there for her when she needed a friend or a fighter- he also restored her faith in herself. He made her see why he loved her. He told her that his love didn’t have to do anything with him and everything with her. He told her she was the one.Meaning both her being the ultimate hero and the one woman for him. And they just slept together. Literally.
Of course when they had to save the world again, he chose to sacrifice himself – to make sure she and everyone else around her made it alive. Well, she was reluctant to let him ago, but did let go at his insistence. Well, I would never have left him there.

Still, it was the perfect bad boy change of all times. But the thing is: he never lost his sense of style,fun and humor.