and yet he's perfectly defeatable with whatever earth can throw at it... while in dbz the best weapon on earth can't even scratch some1 like yamcha... And while radiation isn't really explored in DBZ it doesn't really mean it can do anything to the Z fighers and especially to some1 like Goku that transcended the laws of physics so many times that he's basically god without the ability to actually create stuff... Heck even if Godzilla did manage to destroy his body Goku could still come back as a spirit and kill it... That is ofc assuming that it can even scratch him, which again I really doubt.