Dark and Tormented. A hero needs a driving force behind them, and heroes don't hav eto be heroes. They have to have a dark force that gives them edge. They will not spare anyone to do what he has to do. Like Rorshach from the Alan Moore comic, Watchmen, you have to be tormented to be affective. It keeps you from cracking under pressure.
"No one leaves the building" (man walks out in the background.)