The term "big kahunas" is a slang reference to someone who is brave or powerful. Antonyms for this phrase could include timid, fearful, weak, or powerless. People who are shy or lacking in confidence might be considered opposite to those with "big kahunas." Additionally, someone who is submissive or meek could be seen as the opposite of someone with a strong and assertive personality. The term "big kahunas" may also be related to business or leadership, so words like indecisive or uncertain could also be considered antonyms in that context. Overall, the antonyms for "big kahunas" generally relate to qualities of weakness, timidity or lack of assertiveness.