The phrase "most even-steven" refers to something that is very fair and balanced. Its antonyms would be words that describe things that are uneven or biased. Some possible antonyms include: unfair, biased, lopsided, unequal, disproportionate, tilted, uneven, partial, unjust, and one-sided. These words describe situations where one side has an advantage over the other, or where one group has been favored over another. By contrast, being "even-steven" implies that everyone has been treated fairly, and that there is no bias or favoritism involved. It is important to strive for fairness and balance in all aspects of our lives, and to avoid situations that are unfair or unjust.