"Did one thing" is a phrase that implies a certain level of focus or accomplishment. However, in language and conversation, it can be helpful to have antonyms or opposites of this phrase to convey other meanings. Opposite phrases of "did one thing" include "did nothing", indicating a lack of action or motivation, or "did everything", suggesting that someone took on too many tasks or responsibilities. Other antonyms could be "did the wrong thing", indicating an incorrect or harmful action, or "did multiple things inefficiently", implying a lack of focus or attention. As with any language, having a range of vocabulary and antonyms helps to add depth and convey nuanced meanings.