The phrase "most all-knowing" suggests an individual possessing an exceptional level of knowledge, wisdom, and insight. Its antonyms could be terms such as ignorant, unintelligent, clueless, unknowledgeable, and naive. These antonyms convey the opposite meaning of the original phrase, indicating a lack of knowledge, expertise, and awareness of the subject matter. Other antonyms for "most all-knowing" might include dim-witted, dense, foolish, simple, and dull. Using these antonyms in context could help to describe a person who lacks the necessary knowledge or understanding to make informed decisions or provide meaningful insights into a particular topic.