The phrase "are a par" means that two things are equal or comparable in some way. Some antonyms for this phrase could be "dissimilar," "unequal," or "incompatible." Other possible antonyms might depend on the specific context in which the phrase is used; for example, if discussing performance or ability, words like "inferior," "unskilled," or "incompetent" could be used as antonyms. On the other hand, if discussing relationships or personalities, words like "opposite," "contrasting," or "conflicting" might be more appropriate. In any case, antonyms for "are a par" would indicate that the two entities being compared are not the same or cannot be compared equally.