[n] a bold outlaw (especially on the American frontier)
desperate criminal
apache, assassin, assassinator, badman, bandit, betrayer, bloodletter, bloodshedder, bravo, bucko, bully, bullyboy, burker, butcher, button man, Cain, cannibal, convict, criminal, crook, cutthroat, deceiver, desperate criminal, devil, double-dealer, eradi