The term 'highest-ranking' is used to describe someone or something that is at the top of a hierarchy. The crossword solutions for this term are SUPREME (7 letters), ALPHA (5 letters), and SENIOR (6 letters). SUPREME is an adjective meaning the highest in rank or authority, while ALPHA is a noun referring to the first in a series or the most dominant person in a group. Lastly, SENIOR is an adjective meaning higher in rank or older in age. All three words can be used to describe someone or something that is the highest-ranking.