The phrase "did a bang up job" expresses excellent and impressive performance. Its antonyms, on the other hand, are words or phrases that suggest poor, mediocre, or unsatisfactory performance. Some antonyms of "doing a bang-up job" include "failed miserably," "fell short," "did a poor job," "performed disappointingly," "messed up," "made a mess of things," and "botched the job." These antonyms remind us that sometimes, despite our best efforts, we can fall short of our goals and expectations. However, we can use these experiences as opportunities to learn, grow, and improve our skills and abilities, so we can do a bang-up job next time around.