A person or action that degrades others, hurts them, or is bad for others, which is only done for whomever's personal benefit or happiness.
Person 1: Did you see what Simon Cowell said to that little girl preforming?
Person 2: Yeah, pretty much everybody knows about it. He's such a scumbag.
As a boy in New York during the 1950's, a scumbag was a used condom lying in the street, or in any other public place, usually thrown from a moving car. It signified utter and disgusting worthlessness.
Stay away from him. He's a real scumbag.
A person who gives little care for anyone. Someone who enjoys giving pain to others meanwhile they can't take any to themselves. They enjoy backstabbing their "friends" and jewing them for money.
Hey, you know that kid Chris? He's a total scumbag.