Worst one I ever saw was a question to prove something that was vacuously true if you got the preceding question correct. People spent ages trying to find thei

Worst one I ever saw was a question to prove something that was vacuously true if you got the preceding question correct. People spent ages trying to find their mistake. I was one of the first to finish because I quickly concluded I wasn't going to find the mistake (after checking a mere 3 times).