Antonyms for the phrase "doing one's best" can be interpreted in various ways, depending on the context. Some common antonyms for this phrase include "slacking off," "not trying," "being lazy," "half-hearted effort," and "half-baked approach." The opposite of "doing one's best" could also be considered as putting in minimal effort, underperforming, or simply not being motivated enough to achieve success. Regardless of the antonym used, it is clear that not putting in the effort required to complete a task or achieve a goal is the opposite of doing one's best. Those who strive to put forth maximum effort will always stand out from those who settle for less.