In ancient rome, during times of turmoil, one leader with absolute power would be selected to rule temporarily. this leader was called a

Dictator

Explanation:

Dictator was the title of a magistrate of Ancient Rome appointed by the Roman senate to rule the state in time of emergencies. In the modern sense, it refers to an absolutist or autocratic ruler who solitarily assumes power over the state (although the term is not applied to absolutist monarchies).

Dictator was the highest extraordinary magistrate in the Roman Republic. He was also called Praetor Maximus and Magister Populi.