In what type of government does only one person have all the power?

An autocracy is a form of government in which one ruler has absolute control and decision-making power. Autocracies have existed since ancient times, when kings and emperors ruled over great countries and tribal lands, and they exist today in the form of absolute monarchies and dictatorships. Unlike in a democracy, the people living in countries with autocratic governments have no say in determining the nation’s laws, or in how those laws are enforced. An autocratic ruler is accountable to no one; there is no system of checks and balances, no constitutional limit on the ruler’s power, and the ruler is not held accountable by a cabinet of advisors, a system of courts, the people, or the press.

Source: National Geographic