The Silent Guardians!
Great Big Robot
it's a geat big robot (but not a giant robot monster)
Created by the Mad Thinker, the Great Big Robots are great big robots covered with spikes and armor. They are festooned with weaponry, including a flamethrower, spike shooters, and an electrical field. The Mad Thinker uses them for various tasks. The Silent Guardians have tangled with them a time or two, and haven’t had much luck.