The phrase "most lessened" refers to something that has been reduced or diminished to the greatest extent possible. Antonyms for this phrase include "most increased," "most enlarged," "most augmented," and "most expanded." These words describe actions or processes that lead to the growth or development of something, rather than its reduction. Other antonyms for "most lessened" could include "most abundant," "most plentiful," "most numerous," or "most profuse," as these describe situations where there is an abundance of something rather than a scarcity. Overall, antonyms for "most lessened" are words that express the opposite of decreasing, shrinking or diminishing.