Most off base is generally used to describe a statement or action that is completely wrong and inaccurate. Therefore, some antonyms for this phrase could be "spot on," "accurate," "correct," "right," or "precise." These words imply that the person's statement or action is reasonable and well-founded. Other potential antonyms to "most off base" might be "relevant," "factual," "valid," or "sound," which also suggest that the claim or action is grounded in reality and supported by evidence. Overall, antonyms for most off base convey the idea of a statement or action that is accurate and reliable rather than misguided or incorrect.