The phrase "am on a par" typically means to be at the same level or of equal status with someone or something else. So, for antonyms of this phrase, we can look for words that connote unequal or disparate status. Some possible antonyms might include: inferior, substandard, lesser, or subordinate. Additionally, words like "below par," "uneven," "unmatched," or "unbalanced" could also serve as antonyms for "am on a par." Depending on the context, other antonyms could include words like "unequal," "failing," "weak," or "deficient." Whatever the context, antonyms for "am on a par" convey a sense of disparity or difference in rank or value.