i would have to go with billy grey. when johnny k came to execute him, he was very accepting of his fate. "checkmate dude. come on, get it over with. do it!" johnny was obviously hesitant to shoot him. "i'm doing it!" but billy just wanted to get his death over with and encouraged johnny to pull the trigger. "c'mon, you waiting for a speech or something? do it!" he is also the only character who tried to fight back in his execution. that was badass. i can't forget his speech about jason either. "jason was a law-breaker, trouble-maker, beer-drinker and hell-raiser. in short, the kind of man i want to be."
officer tenpenny and ray bulgarin (that's right, bulgarin) are also good candidates for the most badass antagonists.
tenpenny was voiced by samuel l jackson so he is automatically badass. bulgarin may have been annoying at first, but when he shows you the box with the cook's head, it was fu*king scary. even luis got scared, and he is a hardened criminal.