Detroit Lions 0-16
ANSWER
If you're talking about all-time winning percentages among current NFL teams, it's the Houston Texans, who were 49-79 all-time (.383) going into the 2010 season.
Through the 2007 season: According to the Pro Football Hall of Fame, the worst playoff winning percentage for an NFL team is .250 (2-6) for the New Orleans Saints. The Arizona Cardinals are at .286 (2-5), the Kansas City Chiefs are at .381 (8-13), and the Cincinnati Bengals are at .385 (5-8).
Well for a single season I would go with the Detroit Lions as having the worst single season in NFL history, having had laid a goose egg in the wins column, they became the first team to lose every game in the 16-game season era. But just for bonus points we can't for get the 0-26 Tampa Bay Bucs. This team was the epitomy of futility. In their inargural season they went 0-14 with an average of 9 points per game, but just to keep the streak going they started the next season with 12 more straight losses. They finally won their first game against the New Orleans Saints.
That would be the 2003 Oakland Raiders. The Raiders lost Super Bowl XXXVII, played January 26, 2003 to the Tampa Bay Buccaneers and then had a 2003 regular season record of 4-12.
The Detroit Lions have been called the worst team for this decade.
The 2008-2009 Detroit lions (0-16)
Lions
The 1988 San Francisco 49ers, the 2007 New York Giants and the 2010 Green Bay Packers all had a 10 - 6 regular season record and won the Super Bowl.
new Orleans saints or the jacksonville jaguars
st Louis browns
2010-11 Celtic
That would be the 1899 Cleveland Spiders (National League) whose record was 20-134.
colts
The 1988 San Francisco 49ers, the 2007 New York Giants and the 2010 Green Bay Packers all had a 10 - 6 regular season record and won the Super Bowl.
The Houston Texans, with a record of 2-14, had the worst season in the 2013 NFL regular season.
new Orleans saints or the jacksonville jaguars
Pittsburgh
because its the steelers vs the seahaws.. and the seahawks suck!!!
The 1956 team had the worst overall record in Yankees history. This was followed by the 1972 team.
2008 Detroit Lions: 0-16
st Louis browns
88
2010-11 Celtic
Bruins