The phrase "most accessory" is usually used to express the degree of importance or relevance of a particular item or object in relation to a particular situation or event. However, when considering its antonyms, it is important to focus on words that can convey the opposite meaning of the phrase. Some possible antonyms for "most accessory" could include terms such as "least important," "least influential," "least relevant," "inconsequential," "irrelevant," or "unnecessary." Each of these antonyms can be used to describe situations or objects that have little or no impact or significance in a given context.