Authoritarianism is characterized by the concentration of power in the hands of a single individual or group, who exercise absolute control over all aspects of society.

Adolf Hitler is often considered to be the archetypal authoritarian leader due to his extreme centralization of power, his use of propaganda and terror to maintain control, and his aggressive expansionist policies.

A junta is a military government, typically composed of a small group of military officers, that seizes power through a coup d'état.

Brazil was ruled by a military junta from 1964 to 1985, during which time the military suppressed political dissent and implemented economic policies that favored the wealthy.

An autocracy is a political system in which the ruler has absolute power and is not subject to any constitutional or legal constraints.

Pol Pot was the leader of the Khmer Rouge regime in Cambodia from 1975 to 1979, during which time he implemented a radical communist ideology that resulted in the deaths of an estimated 1.7 million people.

A one-party state is a political system in which a single party holds all political power, typically through the suppression of opposition parties and the control of the media.

China was ruled by a one-party state under the Communist Party of China from 1949 to 2018, during which time the party maintained tight control over all aspects of society.

A diarchy is a political system in which the military and civilian authorities share power, typically through a power-sharing agreement or a coalition government.

Pakistan was ruled by a diarchy from 1958 to 1960, during which time the military and civilian authorities shared power under the leadership of President Ayub Khan.

Tyranny is a political system in which the ruler is not subject to any constitutional or legal constraints and exercises absolute power, typically through the use of force or intimidation.

Idi Amin was the tyrannical ruler of Uganda from 1971 to 1979, during which time he implemented a reign of terror that resulted in the deaths of an estimated 300,000 people.

An autocracy is a political system in which the ruler is not subject to any constitutional or legal constraints and exercises absolute power.

Joseph Stalin was the autocratic ruler of the Soviet Union from 1924 to 1953, during which time he implemented a brutal regime that resulted in the deaths of millions of people.

A dictatorship is a political system in which the ruler is not subject to any constitutional or legal constraints and exercises absolute power, typically through the use of force or intimidation.