And then there’s Spike.

He apologises for the Buffybot; he openly admits that he’s a monster. After his assault on Buffy, the first thing he does is try to redeem himself, because unlike every other man she’s ever slept with, he admits he’s done something wrong, and that he, Spike, is the culprit. And it’s not silent redemption, either: the guilt drives him mad, and when he comes back at the start of S7, not only the audience, but Buffy herself is left in no doubt that what he’s done – regaining his soul – has been an act of atonement: that he’s given himself a conscience, punished himself physically and mentally, and returned with no expectation of forgiveness to offer what help he can. And that, I think, despite everything, is at the core of why I keep coming back to Buffy and Spike’s relationship, why I can’t let go of it: as brutally fucked up as their history is, and despite the fact that Spike’s assault is arguably* the worst thing any partner has ever done to her, he’s also the only parter to accept responsibility for his actions, and to try and directly atone for them. Spike learns because of Buffy; he becomes a better man – or a better monster – through loving her, and I don’t think that’s true of any of the others; even Angel.