There are several antonyms for the phrase "catch one short," which usually means to find someone lacking or unprepared. The opposites of this phrase could be "catch one long," which could imply that someone is fully prepared or has an excess of resources. Other antonyms could include "catch one ample," "catch one thorough," or "catch one complete." These words suggest that someone has everything they need and are fully equipped for the situation at hand. Additionally, the antonym "catch one off guard" could imply that someone is surprised or caught unprepared, but in a positive way, such as by a pleasant surprise or unexpected opportunity.