A tyrannical ruler wields absolute power and authority, and often wields that power unjustly, cruelly, or oppressively.
First used in the 1530s, the adjective tyrannical stems from the late-14th-century word tyranny, meaning "cruel or unjust use of power," which has origins in the Greek work tyrannos, meaning "master." Tyrannical rule is the opposite of democratic rule, which places the power in the people, the majority of whom makes the decisions. Adolf Hitler, Benito Mussolini, and Joseph Stalin are three examples of the 20th century's most tyrannical dictators.