The phrase "is one case" implies a specific example or instance of something. Its antonyms, on the other hand, suggest an alternative or opposite idea. Some possible antonyms for "is one case" include "not a singular example," "common occurrence," "multiple instances," "varied cases," or "a range of possibilities." These antonyms suggest that the situation being referenced is not unique, but rather a part of a larger pattern or trend. By using antonyms such as these, one can express a broader perspective or challenge the assumption that something is isolated or exceptional.