The antonym for "out-shines" is "under-performs," which means to do less well than others or to fail to meet expectations. Another possible antonym is "outdone," which means to be surpassed, exceeded, or beaten in achievement. Other antonyms for "out-shines" might include "inferior," "lackluster," "mediocre," "subpar," "unimpressive," or "inadequate." Whatever the antonym used, it indicates a failure to achieve or to shine as brightly as others, whether in terms of performance, quality, or merit. When looking for the opposite of "out-shines," it's important to identify the negative connotations associated with the word and to find an antonym that adequately reflects those connotations.