overlord

A lord having power or supremacy over other lords.

One in a position of supremacy or domination over others.

One who is lord over another; a feudal superior; a master; specifically, in reference to early English history, a king of one of the Anglo-Saxon realms who enjoyed a preëminence or authority over certain other kings or chiefs.

One who is lord over another or others; a superior lord; a master.

A ruler of other rulers.