The phrase "does one best" implies that a person is doing their utmost to achieve a particular task, but what about when someone is not performing at their best? In such situations, antonyms for "does one best" include "underperform," "fall short," "underachieve," "underdeliver," or "disappoint." These words carry a negative connotation and can indicate that the person did not meet their expectations or potential. They can also suggest that the person lacked the necessary skills, knowledge, or experience to excel in their task. Conversely, positive antonyms for "does one best" include "overachieve," "exceed expectations," "outperform," or "excel." These words highlight success and can indicate that the person went above and beyond what was expected of them.