The antonyms for the word "most confirmatory" can be "least convincing," "least affirming," or "least validating." These antonyms suggest a lack of agreement or certainty about a given statement, theory, or hypothesis. When evidence is weak, ambiguous or contradictory, one cannot be confident that a claim is true or false, and thus it is less confirmatory. In contrast, when evidence is strong and consistent, it is more confirmatory. These antonyms highlight the importance of inquiry, skepticism, and critical thinking in evaluating claims and testing hypotheses, as well as the role of evidence and reasoning in supporting our beliefs and judgments.