Adversarial (adjective)

1. Relating to or denoting a conflict or opposition between two opposing sides or individuals.
2. Relating to or involving an adversary or opponent.
3. Characterized by hostility or opposition.

Origin:

Late 19th century: from adversary, on the pattern of advisory.

Examples:

1. The adversarial relationship between the two countries had a negative impact on their diplomatic relations.
2. The adversarial nature of the competition made the game very intense.
3. The adversarial attitude of the two sides made it difficult to reach a resolution.
4. The adversarial approach to negotiations was not productive.
5. The adversarial system of justice is based on the idea of opposing parties presenting their arguments in court.