The word "unsounder" does not exist in the English language. Therefore, there are no antonyms for this word. However, if the intended word was "unsound," then some antonyms for the word could be stable, secure, reliable, robust, strong, and healthy. The antonyms for "unsound" indicate the opposite meaning of the word, which means not reliable, unstable, sickly, weak, and insecure. In any context, using antonyms for words can help develop a better understanding of the word's meaning and help improve overall vocabulary usage.