idk if this counts but i gotta say my fav would be cerberus. hes a three headed pitbull who is giant and gaurds the gate to the underwould. hes awsome. not to mention i love pit bull.
dont wanna sound rude but cerebus was just a guardian of the underworld NOT a kaiju....however the closest kaiju out there closest to a dog is nun other than king caeser
now i dont know if he looks like a pitbull but he looks like a dog IMO that or a lion but who knows for sure