Antonyms for "gave best shot" might include phrases like "didn't try," "half-hearted effort," or "phoned it in." Other possible opposite phrases could include "gave up too soon," "didn't apply oneself," or "failed to give it one's all." When someone doesn't give their best shot, it can be a sign of lack of interest, lack of motivation, or a lack of confidence. Antonyms for "gave best shot" might suggest that someone didn't put forth enough effort, or that they weren't fully committed to the task at hand. In any case, it's important to strive to always give one's best effort and never settle for mediocrity.