8. New England Patriots (2008)
The Patriots have lost a couple Super Bowls under Bill Belichick. However, this one hurts the most because they came so close to completing a perfect season. Including the playoffs, they entered the game with an undefeated 18-0 record. There was a chance to go completely unbeaten against the New York Giants. Most people hated the Pats but believed the result was inevitable.

However, Eli Manning and his teammate had something to say about that. If any result haunts Tom Brady and Belichick it’s this one because it shouldn’t have happened. Plaxico Burress scored a late touchdown before a Brady sack sealed the deal. The Patriots won so many accolades throughout that season but it felt like they meant nothing after this (via Boston Globe).