Well, first Willow restores his soul, then Buffy has to kill him anyway, the he spends probably hundreds of years in a hell dimension where time runs differently, like a hundred years for every earth day or something, then he comes back so traumatised he's like a wild animal and Buffy has to care for him until he recovers, but yes, he ends up nice again, but they can't be intimate or he'll lose his soul again. It's a very sad tale =(

Thank you.