Most muttered refers to the items, phrases, or words that are repeated frequently in a low tone. However, the antonyms of "most muttered" would be words, phrases, or items that are seldom spoken or said loudly. Synonyms of the word muttered include mumble, murmur, whisper, and grumble, while antonyms for muttered may include shout, cheer, announce, and declare. Words that are shouted or announced are generally not described as muttered. Furthermore, anything that is said loudly can be considered as an antonym for murmurs. In conclusion, while "most muttered" refers to frequently uttered words, its antonyms are the opposite, referring to words or phrases that are rarely spoken or said loudly.