Unicron from Transformers. Damn near unkillable (seriously, he's been decapitated, blown to pieces, had his spark extinguished, etc. and it's only slowed him down), the Transformers equivalent of Satan, unbelievably ancient, "blood" is capable of raising an undead army of Transformers, turns into a planetoid that literally eats other planets, has an insatiable hunger, despises any and all living things, etc.