adjective
A word that describes or modifies a noun or pronoun. In this case, 'adversarial' describes a relationship characterized by conflict or opposition.
The legal system is designed to handle adversarial disputes between parties.
They always seem to have an adversarial relationship with each other.
Their interactions are so adversarial, it's like watching a cat fight.
In nature, predators and prey have an adversarial relationship for survival.