Jacob - my god is he creepy. At first I thought he was a nice guy, a bit bland, but decent. Then I played ME3 where he has some dialogue that weirded me out just a bit, then I found out he automatically cheats if he's romanced and acts like a complete dick about it and then finally I romanced him in ME2 and man, ewww. "Sneaking into the captain's quarters, heavy risk - but the priiiiizzzee." Just eeew.
Carth - Whiny annoying crybaby that is supposed to be a dashing handsome heart throb. No. Because he has the same voice actor he even ruined Kaidan in ME1 and turned me bi -hell yes I'll romance a cute blue babe instead of another whiny Carth.
Assley - yes Assley in ME3, not Ashley in ME1. I mean, I disliked Ash because of her racism and prejudice, but she grew on me. In ME2 both Kaidan and she are a bit annoying, but in ME3 I just don't recognize Ashley anymore. Her personality has changed for the worse, she has gotten silicon implats in her boobs and lips and overall she's just being a total dick. Compared to Kaidan, Ashley is really being mistrustful and stupid and keeps acting like a jerk.
Dawn Star - she just annoys me a lot.
Miranda - she is interesting as a character, I just dislike her because her attitude and Cerberus beliefs.
Everyone in DA2 except Varric. I am really trying to like these characters, because they have aspects of them that are awesome, cute or funny, but they also all have some MAJOR flaw that makes me hate them.
Spoiler filled rant incoming: Aveline is too by the book and her ineptitude with Donnic drives me nuts, Isabela is a selfish, walking STD who started a fcking war because of her greed, Merrill keeps playing around with demons despite getting proof again and again that they are dangerous and she can't handle them, Carver is just a jerk, Bethany willingly submits to the circle after everything her family has done to keep her safe, Fenris talks shit about my sister and just hates all mages because the actions of one, Anders is soooo whiny and depending on your stance in the mages vs templars confilct, he is either annoyingly whiny about his power to right wrongs or a total terrorist nutcase, Sebastian at first seems like a nice guy, but threatens to INVADE Kirkwall with an army if you don't want to kill one of your other stupid friends.
Sten - while being an interesting cool guy, from a RP perspective I just can't overlook him slaughtering an entire family who had saved him because of his beliefs.
Im sorry about the ranting, I just love Bioware games so much and want them and the characters in them to be good.