A lot of characters from RID(01), S4 of the G1 cartoon and a lot of characters from the Unicron Trilogy I did not like one bit but enjoyed the toys. I'm don't think there has ever been a character I've ever hated enough to make me bypass a toy I wanted, though a lot from ROTF like the twins came damn close

I am guilty of buying the odd toy that wasn't much good just because I wanted a representation of the character.

Not having the TF-budget I used to have makes it easier. If its a character I don't like, and most definitely a toy I don't like, I'll just bypass it now. And as others have stated, there are characters I just bypass completely as I have so many already - I've got over 100 different Optimus, I don't need anymore