Captain

A captain is a term for both a military rank as well as the commander of a craft or group. Every branch of the military has a captain rank, usually in command of a company of infantry or ship. The term is used for civilian purposes meaning those who may own their own craft, or is in charge of a group.

History
World War II soldier Steve Rogers was given the name Captain America, though it is unknown if he attained the rank or if it's honorary.

Kalek was a captain in the Kree military before his death at the hands of Galactus.

Nebula and Mentor were captains of their own private ships.