The NFL is home to many intense rivalries, but here are some of the most notorious:

1. Green Bay Packers vs. Chicago Bears: This is the oldest rivalry in the NFL, dating back to 1921. The Packers and Bears have faced off more than 200 times, with the Packers leading the series. The rivalry is fueled by the proximity of the two cities and the fact that both teams have passionate fan bases.
2. Pittsburgh Steelers vs. Baltimore Ravens: This rivalry started in 1996 when the Ravens moved to Baltimore from Cleveland. Since then, the two teams have played some of the most physical games in NFL history. The rivalry is fueled by the hard-hitting defenses of both teams and the fact that they compete in the same division.
3. Dallas Cowboys vs. Washington Football Team: This rivalry dates back to the 1960s and is fueled by the fact that both teams compete in the NFC East. The two teams have faced off more than 120 times, with the Cowboys holding a slight edge in the series.
4. New England Patriots vs. New York Jets: This rivalry dates back to the AFL and has been fueled by several high-profile games and incidents, including Spygate and the Butt Fumble. The two teams compete in the AFC East and have a history of playing close, hard-fought games.
5. San Francisco 49ers vs. Seattle Seahawks: This rivalry started in the 2010s when the Seahawks emerged as a dominant team in the NFC West. The two teams have played some of the most exciting and intense games in recent NFL history, with the rivalry fueled by the success of both teams and the fact that they compete in the same division.