I'm drawn to under-rated things and I hate over-rated things. So naturally, my favorite players are the under-appreciated ones while I despise over-rated football players- particularly those who are only over-rated because of their draft hype.
Right now, my most hated NFL team is the Colts. They were the first team in NFL history last year to go 11-5 with a -32 point differential. So we're talking about a historically flukey season. For whatever reason, the sports media didn't seem to detect this. Arians won coach of the year. Andrew Luck managed more RoY votes than Russell Wilson. Most unforgivably, their GM, Grigson, got exec of the year over John Schneider. The GM who built the NFL's best roster out of nothing and just found a superstar QB in the 3rd round, lost to a no-name, average GM who benefited from a fluke season despite a series of no brainer, cookie cutter decisions to build his (below average) team.
If the Seahawks lose to the Colts next year, it will sting worse than when they lost 21-0 to the Steelers in 2007.
Second least favorite team is probably the Falcons, who basically have 4 good players that carry the whole team. I think they are a good team, but they make my over-rated list. Steven Jackson will still be old and broken down in Atlanta, he's not going to be the difference maker people assume.
Maybe it's sour grapes, but they were extremely fortunate to beat Seattle in the playoffs. It was the ONLY 10 am start of the playoffs, Seattle got 0 points on 190 first half yards, and they somehow blew a lead with 25 seconds to go. It was such a "Seahawky" way to blow a game, so I probably shouldn't hate the Falcons for it, but it still stings. That game cost us a ring, I'm sure of it.
To round out the top 3, I'd probably include the Steelers. We still haven't beaten them, in fact we haven't scored a point on them, since SBXL. Until we get a revenge win, some antipathy will remain.