I actually think he is the opposite. I think he was fiercely competitive and wanted to win. Give him the modern training we get today and he'd be a force to be reckoned with.
I would never call Clarkson uncompetitive (maybe that was some of Monta's problems), just that they (Pistol/Monta/Clarkson) have spent their lives perfecting one skill (scoring) and A) Didn't make it to the level of the best of the best scorers (eg Kevin Durant) B) can't really do anything else at a positive level on an NBA court.