But remember, bro can only lose if he is erased, and he can change the mind, mind manipulation, remember. Plus, he could just trap Godzilla in another universe, counting as a beat.
BUT Bill was summoned by Gideon, which is how he entered Stanley's mind. All someone needs to do is reason with Bill to kill Godzilla from the mind, and boom. And although you're right, there is only one Godzilla that he can kill, and that's the first Godzilla. Bill is shown to manipulate time and space so there