When it comes to antonyms for the phrase "being sufficient," there are quite a few options. Some antonyms one might consider include insufficient, deficient, inadequate and lacking. All of these words (and others like them) imply that something is not enough or is not meeting a certain standard. Another possible antonym for "being sufficient" could be excessive, which implies that something is more than enough and possibly even wasteful. Ultimately, the choice of antonym will depend on the context and the specific qualities of the thing being described.