They had the thunderzords in that time, and they never did anything but get swatted by it.
Also, Serpentera is only a planet buster with a huge charge up time.
Also, which Godzilla is this? Godzilla doesn't have planet busting aoe, but depending on the version, his beams have enough concentrated power to throw off singularities and hurt/kill things that were born in them (space godzilla)
Standard Godzilla from the movies doesn't mean much. There are several different ones.
The original in the very first movie?
The one after that up to the 70s?
Late 80s to 90s?
The ones in the 2000s and up were generally stand-alone movies and not part of one-continuity, except for a few. So there were a handful of Godzillas there, and it ended with Final Wars Godzilla, who is probably the most powerful.