tyrant

A tyrant is an absolute ruler who is unrestrained by law, or one who has usurped a legitimate ruler's sovereignty. Often portrayed as cruel, tyrants may defend their positions by resorting to repressive means. The original Greek term meant an absolute sovereign who came to power without constitutional right, and the word had a neutral connotation during the Archaic and early Classical periods. A government run by a tyrant is usually called a tyranny.