The poker player
Getting Doc's respect isn't easy; you have to succeed in reaching it (by a shot or a punch). But if you manage to do so, you will be able to dictate his actions...until another Bandit steals that respect from you.
Doc is also an Ace at poker. If he drags you into one of his games, you could win or lose big...
With the stakes he is able to win, Doc is easily the richest. We don't call him Doc for no reason.
