The phrase "most forever" implies something that will last for an incredibly long time. The antonyms for this phrase are primarily temporary and fleeting concepts. Some potential antonyms could include "briefly," "momentarily," or "transiently." These words describe things that do not last for long periods and are often short-lived. Another potential antonym for "most forever" could be "impermanent," which describes something that is not permanent or subject to change. Overall, the antonyms for "most forever" convey a sense of impermanence, change, and the fleeting nature of time.