The word "most wasting" refers to something that consumes or depletes resources, time or energy the most. However, some antonyms for this word can be "productive", "efficient", "fruitful", "useful" or "constructive". These words denote something that produces a desired result, uses resources wisely, and generates valuable output or returns. Moreover, words like "saving", "conservative", "economical" and "prudent" are also useful antonyms for "most wasting" as they signify careful use of resources, avoiding unnecessary expenses, or making the most of available assets or opportunities. By using these antonyms, we can communicate positive attributes and achieve desirable outcomes in our personal and professional lives.