adversarial vs oppositional

adversarial

adj
  • Characteristic of, or in the manner of, an adversary; combative, hostile, opposed. 

  • In which issues are tried through the presentation of evidence and argument by adverse parties, with no or limited inquiry by the court's own initiative. 

oppositional

adj
  • Of, pertaining to, or exhibiting opposition 

How often have the words adversarial and oppositional occurred in a corpus of books? (source: Google Ngram Viewer )