Complete Monster/Kirby


 * Yep, you saw it coming - not even Kirby is safe from the wrath of one of these twisted freaks!, the Final Boss of Milky Way Wishes in Kirby Super Star and its remake, Kirby Super Star Ultra, is a total jerk who pretends to be a friend to Kirby in the beginning.  He's serious enough about controlling the planet to qualify as one. He even gleefully admits that he was the one who got the sun and moon to fight so he could pull off his perfect little plan and therefore be able to cause all the mischief he wants. And that's not all: after his first defeat at Kirby's hands, he absorbs some of the parts of Nova, who was blown to pieces after he was sent flying into it, to revive himself as  What a stupid evil punk.
 * What about Necrodeus from Kirby: Mass Attack? He's a skeletal Monster Clown who splits Kirby into ten at the beginning of the game. And if that's not enough, he kills all but one of them, who escaped thanks to the Hero's Heart guiding him. That's enough to make him so completely despicable that, as King Dedede in Kirby of the Stars would say, "This Is Unforgivable!!"
 * And last, but not least, we have Nightmare himself, who, despite his "company support" persona being an Affably Evil Lazy Bum who respects his employees well and just likes to hang out in his lair amusing himself with watching current events, really places himself even more in this spot than any of the listed Demon Beasts/monsters above because he was the one who made them! He eliminated an entire La Résistance group save for a few survivors and likes making monsters and terrorizing planets (Popstar soon to be one of them). Just because he likes doing it. Oh, and he even sped up the asteroid Gerath's course to crash into Popstar itself. Ho boy.