Antonyms for the term "most good for nothing" would be phrases such as "most valuable" or "most useful." These antonyms highlight the positive aspects of an object or person, rather than their perceived worthlessness. Other antonyms could be "most practical" or "most essential," which suggest that the thing in question is necessary or beneficial in some way. Alternatively, you could use antonyms such as "most productive" or "most efficient," which suggest that the object or person in question is capable of achieving or producing a lot with minimal effort. Overall, the choice of antonyms will depend on the context and the desired emphasis.