Definitely bottom 3 or so (it's hard to top the 76ers frankly). And I'm saying this as a Browns fan.
This was great. So many (awful) memories. Although honestly, I put the 2002 Steelers playoff game at number 2 minimum (5 is way too low). That was the only chance in 15 years the team had to do anything worthwhile, and they blew it in spectacular fashion. So painful to remember.