Astaroth

He is the nemesis of the knight Arthur, being the final boss from Ghosts 'n Goblins and reappearing as a boss near the end of Ghouls 'n Ghosts, Super Ghouls 'n Ghosts, Ultimate Ghosts 'n Goblins, and Ghosts 'n Goblins Resurrection. And you have to kill him by any sword.