Victor, winner, conqueror, champion, vanquisher can all denote one who gains the mastery in a contest, conflict, or competition.
Victor , the more literary term, and winner , the ordinary term, usually stress the fact of defeating one’s opponents; additionally victor can connote a triumph or a glorious proof of one’s powers. The terms are applicable when the test is one of strength, strategy, skill, or endurance.
Conqueror stresses the defeat and subjugation of an enemy or opposing force; the term is seldom used appropriately in respect to friendly games or competitions where winner is the regular term, for it usually presupposes a warlike struggle or an attempt to crush by getting the upper hand.
Champion applies to the one who gains acknowledged supremacy through a contest or in a field of competition (as in an athletic contest or in a given sport). The term does not apply to a winner of any test, but only of a test in which one meets all of those of highest rank in the field or meets the one who holds the title of champion or one who challenges one’s own right to hold that title.
Vanquisher is often used in place of conqueror and, often ironically or somewhat hyperbolically, in place of victor or winner , when there is an intent to imply an overpowering or an overwhelming or crushing defeat.