(n.) One who usurps; especially, one who seizes illegally on sovereign power; as, the usurper of a throne, of power, or of the rights of a patron.

Simon Legree absolute monarch absolute ruler all-powerful ruler arrogator autarch autocrat caesar commissar czar despot dictator disciplinarian driver duce hard master martinet oligarch oppressor pharaoh pretender slave driver stickler tyrant warlord