Megalon

Megalon (メガロ, Megaro?) is a fictional kaiju (giant monster) featured in the 1973 Japanese tokusatsu film Godzilla vs. Megalon, the thirteenth Godzilla film produced by Toho. A beetle-like arthropod, Megalon is the primary antagonist of the film. Godzilla vs. Megalon is one of the most unpopular and frequently criticised of Godzilla films, and Megalon itself plays no small part in that. Despite this, the character has remained a fixture of the popular imagination.

Enemies
In his only movie apperance, megalon would protect it's civilization from anything, so when it was accidentaly the target of nukelear testing, he imediately attack other humans.