potentate

Etymology

From Middle English potentat, from Old French, from Late Latin potentātus (“rule, political power”), from Latin potēns (“powerful, strong”), the active present participle of possum (“I am able”).

noun

1. A powerful leader; a monarch; a ruler.
   She was now one of a group of oriental beauties who, in the second act of the comic opera, were paraded by the vizier before the new potentate as the treasures of his harem. 1900, Theodore Dreiser, Sister Carrie
2. A powerful polity or institution.
3. (derogatory) A self-important person.
4. (humorous) Someone acting in an important role.

adj

1. (obsolete) Regnant, powerful, dominant.