The word "most super-duper" means extremely excellent or fantastic. Its antonyms are words that convey the opposite meaning, such as mediocre, inferior, or subpar. Mediocre implies something of average quality, unremarkable or unexceptional. Inferior denotes something lower in quality or value than others, subpar means not up to the usual standard or below average. Other antonyms that can be used for "most super-duper" are lousy, dreadful, terrible, and awful. These words describe things that are unpleasant, unsatisfactory, or downright bad. In summary, the antonyms for "most super-duper" are words that express low quality, inferiority, or unpleasantness.