The phrase "does one duty" implies fulfilling one's responsibilities or obligations. Its antonyms, therefore, would be words that connote irresponsibility, neglect, and failure. Some of the antonyms for "does one duty" include neglecting duties, shirking responsibilities, disregarding obligations, and avoiding commitments. Other possible antonyms could be slacking off, ignoring tasks, ditching assignments, and abdicating duties. In short, any words or phrases that communicate the opposite of performing one's duties can be considered antonyms for "doing one's duty," a phrase that highlights the importance of fulfilling one's obligations for the common good.