adversary AD-ver-sair-ee noun WS #2

a person, group, or entity that opposes or competes against another; an opponent or enemy

1. The two countries were adversaries and fought against each other during the war.
2. His lack of confidence is his only adversary when it comes to success.
3. She resented it when her office adversary was promoted over her.
4. The chess players have been adversaries for many tournaments.
5. The detective finally confronted his longtime adversary after years of pursuit.