Do you mean bad ass, or bad man?
A bad man would be John Preston (Christian Bale) in Equilibrium. He was THE man when he decided to go on a rampage, completly anihilating the bad guys, and looking good while doing it. He is a bad man because he can abuse his oposition, and is a good guy.
A bad ass i would probably describe as someone like Riddick (Vin Diesel) in the Chronicles of Riddick. He has the ability to be a bad man, but he's not 'good'. Therefor he is a bad ass. He's damned amazing, but you don't really want him to be around unless you have something for him to hurt/mame/kill that isn't you.
Not too sure if that helps, but thats about the best way i can describe it while slightly tipsy.
