Kinsey in Stargate SG-1, since I'm rewatching the show and keep having to see that raging twat all the time atm.
I'm sure there are plenty others I hate with a passion but I'm apparently too brain damaged to remember now. I guess there are many characters that are supposed to be likeable but I just find insufferable for whatever reason, like Nathan and Elena in Uncharted and Ellie in TLOU (I can't stand the constant witty banter). Can't really be bothered to watch/play something when I'd just like to see the main character killed off asap and knowing it won't happen lol.