When it comes to antonyms for the phrase "most longtime," there are several options to consider. Some possible antonyms might include "recent," "new," "novice," "beginner," or "short-term," among others. Depending on the context in which the words are being used, different antonyms may be more appropriate than others. For example, if you are talking about employees who have been with a company for a long time, the antonym "new" might be a good choice. On the other hand, if you are referring to someone who has just started a new hobby, "novice" or "beginner" might be more fitting. Whatever the case, antonyms can be a useful tool for clarifying meaning and expressing ideas more precisely.