The term "most highest-ranking" can mean the person or thing that holds the topmost position in a particular category or ranking system. However, when we look for antonyms for this phrase, we find words that refer to lower or inferior positions. Some antonyms for "most highest-ranking" include lower-ranked, lower-level, inferior, subordinate, lower-middle, lower-class, bottom-ranking, lower-grade, and lesser. These antonyms indicate that the subject or object is not at the top of the ranking system and may have fewer powers and responsibilities compared to those who hold higher positions.