Opponent (noun)

A person or group that opposes or resists someone or something.

Origin:

From the latin opponens, present participle of opponere ("to set against"), from ob- ("in the way of") + ponere ("to pu.t")

Examples:

1. John and I are opponents in the chess game.
2. The company's main opponents are the other companies in the industry.
3. She had many opponents in her political career.
4. The team's opponents were very strong this season.
5. He is a formidable opponent in the courtroom.