The word "most undimmed" signifies something that is shining the brightest, but what about its antonyms? If we talk about the antonyms, then "dim", which means to become less intense, is the closest word. Another antonym for "most undimmed" could be "dull," meaning something that is not bright or lively. "Obscure" could also be an antonym, referring to something that is hidden or not clear. "Faded" could also be used as an antonym, meaning something that has lost its brightness. Therefore, these are just a few possibilities for the antonyms of "most undimmed.