I would say, believe it or not, Chuck E. Cheese.
Yes, Godzilla does the whole “breathes fire” bit, but that is way over-rated.
I also think that in a ring, his size could work against him.
Chuck E Cheese, much like the pied piper, could call his minions of children in to help.
Plus, there is also the flaming hot pizza trick. Chuck would walk in the arena with a hot mushroom pie (Godzilla is a vegetarian, you know) and the second Godzilla out it in his mouth, BLAMMO, the roof of his mouth is burnt.