The antonyms for the word "most chartered" are "least chartered," "unchartered," and "unexplored." While "most chartered" implies that a location or route has been thoroughly mapped out and explored, "least chartered" suggests the opposite - that a place or path has not been extensively studied, surveyed, or traveled. "Unchartered" is another antonym that implies a lack of mapping or exploration, while "unexplored" specifically refers to places that have not been thoroughly investigated or discovered. These opposites remind us that there is always more to discover and explore in the world around us, and that there are still frontiers waiting to be charted.