What are the opposite words for most knee-slapper?

The term "most knee-slapper" implies something that is incredibly funny or amusing. When looking for antonyms, we can search for words that contrast with this idea. In this case, we could look for words that describe things that are dull, boring, or uninteresting. Some potential antonyms for "most knee-slapper" could be "tedious," "dull," "boring," "uninspiring," or "unfunny." These words describe situations or things that fail to elicit laughter or evoke any emotional reaction. While antonyms for "most knee-slapper" may not be the most exciting words, they help to convey the opposite meaning of what is often considered to be a hilarious experience.