The term "sub best" implies that something is less than the best. It can be challenging to find a perfect antonym for it as it depends on the context. However, some possible antonyms for "sub best" include superb, excellent, fantastic, outstanding, exceptional, first-rate, top-notch, and superior. These words indicate that something is the best or the highest quality. Conversely, some antonyms for "sub best" can be inadequate, insufficient, substandard, mediocre, inferior, and unsatisfactory. These words highlight that something doesn't meet a particular standard or expectation. In conclusion, the antonyms of "sub best" evoke different connotations, contextualized by the use of the word.