antihero
“A protagonist who lacks traditional heroic virtues and noble qualities and is sometimes inept, cowardly, stupid, or dishonest, yet sensitive” (Source: Benet’s, 40).
“A protagonist of a modern play or novel who has the converse of most of the traditional attributes of the hero. This hero is graceless, inept, sometimes stupid, sometimes dishonest” (Source: Harmon & Holman, 30).
Example: Parker in the novels by Richard Stark.
Also see: hero, protagonist.