The antonyms for the phrase "showing gain" could include "showing loss," "showing decline," or "showing decrease." These terms indicate a decrease or reduction in value, profits, or productivity. For example, if a company's financial reports show a loss, it means they did not make a profit in the given period. Similarly, if a person gains weight, they are showing gain, but if they lose weight, they are showing a loss in weight. Opposite of "showing gain," synonyms for the term could be "showing progress" or "showing improvement," indicating growth or advancement.