Vampire. Arucard is a fucking baller. Long live the No Life King. To people saying Titan because they have size, power and only 1 way to die... they also lose any and all sense of reason and humanity, unless you're a Titan Shifter. And Arucard can kill a Titan easily, once he loses a couple souls to find the weakness, he can summon that Baskerville dog bastard thing, and have it tear the nape of the neck, or any other possibilities.