Imperial assault class ang Gun Crusher na ipinakilala sa Season 16, built para sa front-line combat na may high durability at explosive ranged pressure. Si Fisher, batang inagaw at tinrain ng secret Imperial Corps ng MU Empire, ang naging unang Gun Crusher at na-deploy sa Elveland para sa monster annihilation missions. Nagsisimula ang class na may balanced offensive at defensive stats at umuusad mula Gun Breaker hanggang Master Gun Breaker, bagay sa aggressive party setups kasama ang Rune Wizard at Grow Lancer.