Notes:

After Galactus forced Thor to become his Herald and made him watch as he murdered worlds in order to fight an entity called The Black Winter, Thor steals Galactus' Power Cosmic and uses it to murder him and the Black Winter.

Despite the fact Galactus is the ultimate genocide, he's still a part of the Cosmic Balance and killing him will bring consequences. either Reed or Franklin Richards will bring him back to life and he will come back super p----- with the intention to wipe out all sentient life.