I'm one of the nicest, most polite and laid back guys you'll ever meet. But when I have drank enough to be in a blackout situation, I become very aggressive and jealous. My girlfriend has told me numerous times of how she had to physically get between me and some other guy because I was ready to pound on him over some minor infraction (bumped my arm, etc.). She also told me of how she would have to talk our way out of trouble when I would pick a fight with a much larger guy. I, of course, never recalled any of this. And it shocked me, because I am the most non-confrontational person ever (when sober).
I think that when the threshold is crossed, it becomes a Dr. Jeckyll and Mr. Hyde situation. The worst characteristics of your being come to the forefront. I don't ever want to be there again.