Sports Illustrated recounted the most excruciating losses for every NFL team. I'm betting you can guess the most excruciating loss in Tampa Bay Buccaneers history already: the first time they made it to the NFC championship game in literally 20 years, held one of the best offenses of all time to just nine point scored and somehow still lost. Yes, it's the 1999 NFC championship game.
Side note: 1999 season, game played in 2000. Do we call this the 1999 NFC championship game or the 2000 NFC championship game? I don't know. There appears to be no consistency or rule for this whatsoever.