what common human behavior do you hate the most?
Ignorance.
I am annoyed by pride and ignorance as well.
I would also add -- those who live by emotion (who can't think), and those who are malicious. By "malcious" I mean those who willfully victimize their fellow man, either in their person, their property, or their reputation.
All sins are evil before God, but some sins evoke more compassion than others. We're all weak, frail human beings. But malicious? Not at all. Many human beings, even pagans, heretics, and other non-Catholics, try to be "good people". Maliciously slandering, scheming, murdering, and stealing from our fellow man is something that most of us can say we're above (or at least something we COULD be above, with a little effort.)
Of course, ANY mortal sin deserves Hell. And I have compassion on my fellow human beings, with fallen human nature, sinners like myself.
But while human nature requires us to be imperfect, and requires a certain amount of sin and fault, it doesn't require ANYONE to be malicious.
One can easily avoid being an honest-to-goodness villain.To be a villain, you have to WANT IT. It's not human frailty that causes someone to willfully lie about another, exploit the poor, defraud wages, commit murder, etc.