This is a stretch but, if Grimlock
uses some intelligence and his super-strong jaws he can ambush Galvatron. He should lie in wait under cover, such as behind a tall but weak wall. Bursting out, he should crush the cannon immediately, along with the right arm. Straight afterwards, he should crush the head. That should kill Galvatron but, to be safe, Grimlock should bite Galvatron into small pieces. The pieces can be put into standard black bin bags and left for collection by the bin men. They don't contain meat so the fox won't rip open the bags.