And I think the First Evil could have been interesting if they had used it for more psychological torment, but instead it didn't really seem like they knew what to do with it most of the time, other than as an excuse for Sarah to play evil or to bring past favourite villains back. Which is all very well, but as its own entity the First was just never scary

And Xander wasn't badly-written exactly, he just felt more and more pointless to me as the seasons went on, but the writers could never bring themselves to get rid of him. Instead they tried to force his role as the heart of the group and the one who sees. Neither of which made much sense to me, and felt more like the writers wanting to give him some kind of obvious role alongside Buffy, Giles, and Willow. But the heart of the group he was not IMO, just because he made the occasional speech once every 20 episodes or something. Most of the time he was the one in the group who was lashing out at Buffy if anything, and he never struck me as being particularly insightful either. Giles was the one in episodes like Faith, Hope, and Trick who quietly got to the bottom of Buffy's real issues, Xander was just the guy to pop up and lecture her on what a terrible friend or girlfriend she was in Dead Man's Party, Revelations, Into The Woods etc