Antonyms for the word "wast tantamount" include valuable, useful, significant, substantial, and worthy. These words are the opposite of "wast tantamount," which describes something that is wasted, wasted effort, or wasted resources. "Valuable" suggests that something has worth, usefulness, or importance. "Useful" means that something is practical, efficient, or beneficial. "Significant" implies that something has meaning, impact, or relevance. "Substantial" denotes that something is substantial, considerable, or robust. Lastly, "worthy" signifies that something deserves recognition or respect. All of these antonyms convey a positive connotation, which contrasts with the negative implications of "wast tantamount.