The antonyms for the phrase "showed to advantage" would include terms such as "disadvantaged," "obscured," "masked," "veiled," "camouflaged," and "hidden." These words suggest that the subject may not be presenting its best qualities or attributes, and that there may be factors hindering or inhibiting its full potential. Conversely, words such as "enhanced," "highlighted," "emphasized," "flaunted," and "showcased" may serve as synonyms for "showed to advantage," indicating that the subject is presenting itself in its most desirable or impressive manner, likely garnering attention and admiration from onlookers.