There are several antonyms for the word "subbest," which is not a widely recognized term. However, if we break it down, the prefix "sub-" suggests something that is inferior or less than ideal. Therefore, antonyms for "subbest" might include words like superior, excellent, top-notch, first-rate, exceptional, outstanding, or unparalleled. These words describe something that is of the highest quality and exceeds expectations. Conversely, inferior, poor, shoddy, second-rate, mediocre, or substandard might be considered antonyms for "subbest" as they suggest something that is below-average or not as good as it could be.