Antonyms for the word "unpresumptuous" are mostly adjectives that convey traits associated with arrogance and conceit. Some of the antonyms include "presumptuous," which implies showing too much confidence or taking liberties without justification. Another antonym is the word "egotistical," which conveys excessive self-importance and vanity. "Conceited" is another antonym that implies having an exaggerated opinion of one's abilities and showing off to others. Some other antonyms include "cocky," "haughty," "pompous," "snobbish," and "self-important." Overall, these antonyms reflect traits that are opposite to the humble and unassuming nature of someone who is unpresumptuous.