The expression "were of no avail" indicates that something was unsuccessful or ineffective. Therefore, antonyms for this phrase could include terms such as successful, effective, productive, fruitful, useful, beneficial, advantageous, or satisfactory. These words suggest that the outcome was favorable, and the effort put in led to a positive result. Using these antonyms can help convey a different message from the original phrase and indicate that the effort invested was worth it. By using antonyms for "were of no avail," the speaker can convey a positive outcome and uplift the mood of the conversation.