The word "most dirtied" means the most soiled or contaminated, so some antonyms could be "cleanest," "purest," or "sanitized." "Cleanest" means free from dirt or impurities, "purest" means uncontaminated or unadulterated, and "sanitized" means treated or cleaned with chemicals to eliminate or reduce harmful microorganisms. Other antonyms for "most dirtied" could include "sterilized," "hygienic," or "spotless." These words convey the opposite meaning of dirtied, emphasizing cleanliness, purity, and healthiness. Depending on the context, different antonyms could be more appropriate.