A foul mouth.
What is the one thing that would totally put you off someone that you previously thought was hot?
Pick her nose in public. Private nose picking is totally acceptable, we've all done it.
Lack of respect, lack of integrity, lack of honesty, lack of honor.....I know that's four things, but any lack of one of those makes a person "not nice" in my book.
Finding out their dad was the leader of the local KKK.
Lack of anger management and being too egotistical
Being a liar, we all do the white lie thing but just why lie about who you are or what you do?
Cruelty. In any form.
If this person only liked me for how I looked...
Drugs , smoking , booze, bad attitude.
Lack of respect, compassion and manners. As soon as someone starts acting like a jerk, I will let them know how I feel about their behavior and then walk away until they can act better.