Wait until you learn his skill in his skill tree that gives his critical hits the Drain effect. Combo that with his Aura that makes all of his attacks critical hits for a limited time and he becomes a beast. The game really makes sure the player knows that Dunban is the biggest badass in the party. Considering he's one of the few characters who gets actual anti-Mechon melee weapons that don't require the Monado to be useful...