OK. The robot is designed as a missile defense system. You say its armed with missiles. Well, it can carry only so many. Try to figure out a relatviely remote area and have the military bombard it with as much as it can. Not just Apaches, but aircraft, artillery, tanks etc.. The robot will expend all of its misslies in defense.(if it designed for missile defense, it would target and fire at all incoming ordnance and targets) That will take care of its firepower AND should burn off some of its energy. (What is its energy source anyway?) Now study its outer surface. Since we are speaking on comic book robots, they all have some sort of outside access hatch that you can get someone in to and wreack havoc on the inside and stop it.