The phrase "did a turn" is a figurative expression that means to perform or execute an action. Some antonyms for this phrase include "did nothing," "did wrong," "did badly," "did not accomplish," and "did not execute." These antonyms suggest a lack of action, failure or underachievement in completing a task. Other antonyms for "did a turn" might include "did the opposite" or "did something different," which imply a deliberate change in action or direction. Depending on the context in which this phrase is used, the antonyms may be a more fitting description of the action taken.