This was too hard. I voted as a VIEWER as opposed to "which would I get a restraining order against were they to move next door."
Harmony almost makes it, but she wasn't in it enough to bother me...and strangely, a couple of Harmony-centric eps were actually enjoyable to me to cancel out the dislike.
Connor is another close one, but I couldn't help but sympathize with him a bit, and also can't help but feel he was written more as a plot device than an actual character which also makes me sympathize with his character in a meta-way. His demeanor in season 5 also makes up for it.
I dislike the Trio made into the Big Bads of season 6. I wouldn't mind an arc of them, but their presence was too much, especially as they're so one-note, even if some bits of dialog (plus painting the Death Star on their secret van with arguments over if it was done right) make me laugh (offhand, my favorite being where they forget to spy on the Slayer because they get so into their argument on who the best James Bond is).
If you want to go for real life is the Big Bad (which I think s6 did very poorly, with even s5 before it doing a better job without even trying) it's not like most get targeted (even beaten up) by geeks (note, I consider myself a geek) It just got burdensome to watch, and unlike some of the other burdensome aspects of season 6, there was nothing really to make up for it before or after (Warren in season 5 was just enough Warren without getting on my nerves to watch it, but I still wasn't much of a fan, and I've always been neutral about Jonathan overall).
Though I did like the Buffybot arc (which I bring up since Warren made that possible)...but I expect many hate that one. Though the crowning moment of that for me was Buffy gritting out, "You couldn't tell me apart from a robot!?" (Guess Tara lost some of her psychic senses, but I can't remember if she actually saw the Buffybot or just heard about it). And after the crowning moment, the Buffybot is used well, storytelling wise.
I'm going to count the Trio as one entity, so two more...Flutie, and whatever lawyer that Faith beat up really bad (glad we didn't get too much of him, though he was an important component to more than one story for me to dismiss as a very minor character).
Snyder is a horrible toad (no insult to toads intended), but he was a fun foil as well (speaking as a viewer) who played his part well. I'm happy with him getting eaten by a snake, but I took way too much pleasure in Flutie being eaten early on, despite that Flutie (unlike Snyder) did seem to genuinely mean well. Flutie really rubbed me the wrong way and was funny for maybe the first 5 minutes.
I'm refusing to let myself think of season 7 (despite a few redeeming moments of it, ALL of it early in the season for me, I won't even give credit for the speech at the end since there really wasn't a choice to be made). I'm also ignoring one-shot or very minor characters that I liked or hated or felt meh about.