a sovereign or other ruler who uses power oppressively or unjustly.

any person in a position of authority who exercises power oppressively or despotically.

a tyrannical or compulsory influence.

an absolute ruler, esp. one in ancient Greece or Sicily.

noun

democrat

noun

absolute ruler , absolutist , authoritarian , autocrat , bully , despot , dictator , hitler , inquisitor , martinet , oppressor , slave driver * , stalin , big brother , fhrer , man on horseback , strongman , totalitarian , autarch , caesar , czar , overlord , persecutor , tsar , usurper