The phrase "most begrimed" implies that something is heavily soiled or dirty. Antonyms for this phrase would be words that describe cleanliness and purity. Some options could include "pristine," "immaculate," "spotless," and "untarnished." These words suggest a lack of dirt or grime, and therefore are the opposite of "most begrimed." Other antonyms could include "sanitary," "hygienic," "cleanly," and "sterile." These words portray a sense of cleanliness and suggest that something is free from harmful bacteria or other contaminants. Ultimately, the antonyms for "most begrimed" convey a sense of cleanliness and purity, rather than dirt or grime.