Makoto, he is a empty puppet who from a neutral stance goes towards the boring one. Game kinda leads him to be a perverted idiot, even if you point him in a right direction he is more like a freaky robot then anything. Then again, most of cast in that game has questionable common sense with depressing feeling around them so I don't know...
Aside from that, any too-perverted MC jerk. I rarely have problems with main girls or side characters, but when I have to listen/read to MC's crap or when he is abusing girls, then it's just not enjoyable for me.