The word "most many-faceted" refers to something that is complex and has many different aspects. However, its antonyms would describe something that is simple, straightforward, and has only one dimension. Other antonyms could include words like limited, singular, one-dimensional, or uncomplicated. When speaking about a person or personality, the antonyms for most many-faceted would be narrow-minded, one-track, or simple-minded. By using antonyms, we can describe a wide range of things that contrast with most many-faceted, giving more nuance and variety to the English language.