An ugly personality really turns me off. It's not entirely easy to describe what I mean with this. I'll give some examples.
People who are cruel. Not to me in particular, but to anyone. Nobody likes a jerk.
People who are constantly bitter and cynical. Not attractive one bit.
People who think it's okay to be ignorant.
People who justify their weaknesses as personality traits. No, you do not have frail nerves, you have a phobia and you're using your "frail nerves" to chicken out of dealing with it. Grow some balls and man the hell up.
People who lie and try to get off on semantics rather than apologizing when the truth comes out.