The word "most compulsatory" implies something that is extremely mandatory or necessary. Its antonyms, therefore, would be words that describe something that is not required or even optional. Some possible antonyms for "most compulsatory" include voluntary, discretionary, noncompulsory, elective, and optional. These words suggest that something is not a strict obligation or a must-do action but rather a choice that can be made based on personal preference. While "most compulsatory" may be associated with rules, laws, or duties, its antonyms give room for flexibility, independence, and freedom of choice.