The antonyms of the word "most vanquishing" would be words that denote weakness, failure or inferiority. Some possible antonyms of the word most vanquishing include losing, surrender, conceding, giving up, accepting defeat, backing down, powerless, feeble, frail, and impotent. While most vanquishing implies a triumph over an opponent, its antonyms refer to the opposite side of victory, defeat, and loss. These words depict a scenario where victory is far from reach and defeat is inevitable. When we encounter such antonyms, it's important to remember that setbacks and failures are just a part of life, and with resilience, we can always rise above them.