The phrase "was tardy" implies lateness or delay, and it can have various antonyms depending on the context. If one is referring to being delayed in arriving at a destination, some antonyms can include "was punctual," "arrived early," "was on-time," or "showed up promptly." If one is referring to completing a task or assignment, antonyms for "was tardy" can include "was prompt," "got things done quickly," "finished tasks ahead of time," or "didn't waste time." In any situation where time is a factor, antonyms for "was tardy" essentially refer to being efficient, reliable, and getting things done on time.