The phrase "most darling" implies a strong affection or endearment towards something or someone. Its antonyms would therefore imply a lack of affection or even disdain. Some possible antonyms for "most darling" could include "most reviled," "most detested," or "most loathed." These words suggest a strong negative sentiment towards the subject at hand. Other antonyms for "most darling" might include "most disliked," "most unpleasant," or "most unappealing." Regardless of the specific antonym used, the phrase "most darling" implies a fondness or warmth that is starkly absent from its opposite.