The antonyms for the word "most gut-busting" would be words that mean the opposite of funny or hilarious. Some of the antonyms for "most gut-busting" could be terms like humorless, unamusing, boring, uninteresting, unfunny, or unfunny. If something is not gut-busting, it may be a bit dull or uneventful. It may not elicit laughter or joy from those who experience it. Additionally, "most gut-busting" suggests that something is incredibly funny, so antonyms may highlight the lack of humor or entertainment value. Ultimately, the antonyms for "most gut-busting" will focus on the absence of humor and any associated positive feelings.