2015: Kansas City Chiefs
This was a surprise as the Chiefs had been a competitive team in 2013 and 2014. No one could believe they started the 2015 season 1-5, but they created a big hole to dig out of. But they did so in impressive fashion.
Starting with a 23-13 victory over the Pittsburgh Steelers in Week 7, the Chiefs won their final 10 regular-season games and went into the playoffs as a team no one wanted to face.
That was proven in the Wild Card round as they pounded the Texans, 30-0. The following week in the divisional round, they went down to Gillette Stadium and gave the New England Patriots all they wanted, eventually losing 27-20. But good things were coming to Kansas City and the team has never looked back since.