For me it will always be the Ravens. The Ravens represent everything that is wrong in sports. Art Model took a well supported team out of Cleveland and moved them to Baltimore. If you remember there we three cities vying for expansion. Charlotte, Jacksonville and Baltimore. Modell sat on the expansion committee. He made sure the NFL didn't pick Baltimore so he could swoop in an take the deal. The NFL made him leave the name and colors behind and eventually had to put a team in Cleveland which they returned the name and colors to.
Modell was a greedy bast@ard. And Baltimore, of all cities (who knew what it was like to have a team ripped away from them), didn't care. The Governor of Maryland, Glendenning, was so desparate to have a team, gave Modell a sweatheart deal. It was so over the top, that the MD legislature stepped in and curtailed some of it.
Baltimore should have had the Jacksonville franchise. If they had gotten it, I would probably have made them my second team to watch after Buffalo. But the way they stole the Browns, and the way people reacted here with indifference to the suffering of Cleveland fans, made them my lifelong most hated team. And then don't get me started on Ray Lewis.