In many ways my first Kirby monster was Mangog. (Technically the first was Fin Fang Foom in the pages of Fantasy Masterpieces.) Unleashed in the pages of Thor #154 the grotesque Mangog was set to march on Asgard and bring down Ragnarok by drawing the Odinsword from its massive scabbard.
He's an impossibly extreme creature, with an enormous head and clutching claws capable of crushing Asgardians on a whim.
The combined hate of a billion billion beings, Mangog was an unstoppable force bent on utter destruction.