The phrase "on one's case" typically means that someone is bothering or criticizing another person. Antonyms for this phrase could include "off someone's case," "leaving someone alone," "praising someone," or "supporting someone." When someone is "off someone's case," they are not bothering or criticizing that person. When someone is "leaving someone alone," they are not interfering with or bothering that person. When someone is "praising someone," they are expressing approval or admiration for that person. When someone is "supporting someone," they are helping or encouraging that person. By using these antonyms, we can convey the opposite meaning of the phrase "on one's case.