I'll go Chicago Bears:
1) Lowballed Lovie Smith for a while before finally caving and paying him. Why mess with the guy if you're going to end up paying him anyway?
2) Let Ron Rivera go without hardly batting an eye. He orchestrated that awesome D, and is now merely the LB coach in San Diego. WTF?????
3) Let Thomas Jones get away, and are now going to rely solely on oft injured, fairly unproven Cedric Benson, who apparently isn't a locker room favorite either. They didn't get the memo that it's a two-back league.
4) Tank Johnson got suspended 8 games
5) The whole Lance Briggs fiasco- I'm not even gonna start on that
6) They signed Archuletta!! HAHA
7) They lost the Super Bowl- never good for teams the following season
My runner-ups: Miami, Buffalo, Atlanta, Pittsburgh
Here's a good article discussing this exact topic:
FOX Sports on MSN - NFL - Worst to first: Ranking the NFL off-seasons