Hmm. I can't really think of much.
I guess I'll go with the Thieves Guild quest line in Oblivion. Not sure I'd say I despise Oblivion though (especially not the same way I despise the so-called sequel to Diablo), just that I don't enjoy it.
I could also say Van Cleef in WoW, but again I don't really hate the game. It's just boring. Actually it does have a few levels I used to enjoy a lot. Scarlet Monastery, for one. And I know I'm weird for saying it but, I frikkin liked Gnomeregan. Almost wished I could cap my leveling off at 40... never did like the endgame stuff.