* Melancholy refers to a feeling of pensive sadness, often without a specific cause. It evokes a sense of gloominess and dejection.
* Fantastic means extraordinary, remarkable, or imaginative. It suggests something impressive, exciting, or surreal.
While melancholy implies a negative emotion, fantastic generally implies a positive or at least neutral one.
Therefore, melancholy and fantastic are not opposites and cannot be considered antonyms.