Antonyms for "be on a par with" would include phrases such as "inferior to," "below average," or "fall short." These phrases indicate a lack of equality or similarity in comparison to another person or thing. Other antonyms could include "behind the curve," "outmatched," or "substandard," all of which convey a sense of being left behind or being inadequate in some way. These antonyms can be useful in describing a situation where there is a clear hierarchy, or where one person or thing is clearly better or worse than another. Despite the negative connotations, acknowledging these differences can help us to set goals for improvement and work towards achieving a higher level of success.