http://www.ranker.com/list/the-ten-worst-teams-ever-to-win-the-superbowl/rp59,
2001 New England Patriots
The 2001 New England Patriots gave birth to a dynasty in a league whose rules, it was believed, made it impossible to maintain a dynasty. In 2001, the Patriots were not the hated perennial contenders that they would later become. The season before they had gone 5-11 and finished dead last in the AFC East. In the second game of the 2001 season, Drew Bledsoe went down with a season-ending, career-ruining injury and was replaced by a relative unknown sixth-round draft pick from Michigan, Tom Brady. Brady may have led the Patriots to an 11-5 record, an AFC East championship, and, eventually, the Super Bowl, but 10 games into the season the team was only 5-5. The defense was ranked 24th in a league of 31 teams, and the Patriots easily could have lost each game of the 2001 playoffs. The now-infamous "Tuck Rule" nullified a potential Brady fumble and lifted the Patriots to a 16-13 overtime victory over the Oakland Raiders in the divisional round. In the second quarter of the AFC Championship, Brady went down with an injury of his own, being replaced by Drew Bledsoe who was 3-3 passing and nothced one touchdown to give the Patriots a 14-3 halftime lead. In the second half, a Patriots kick was blocked, but recovered by receiver Troy Brown who threw a lateral pass to Antwan Harris, who ran 45 yards for an unbelievable touchdown and extending the lead to 21-3. The Steelers fought back to within a touchdown, but were unable to overcome the opportunistic Patriots, who won 24-17. In Super Bowl XXXVI, the Patriots were outgained by 200 yards by the "Greatest Show on Turf" St. Louis Rams, but the Rams turned it over three times, leading to 17 of the Patriots 20 points. Nevertheless, it still took a long, last-second field goal by Adam Vinatieri to complete the storybook season. While the story may be one of the most improbable in NFL history, the fact remains that the 2001 Patriots were simply not the best team that season.
2005 Pittsburgh Steelers
The 2005 Pittsburgh Steelers posted an 11-5 record, finished second in the AFC North to the Cincinnati Bengals, and won Super Bowl XL. In the AFC Divisional Playoffs against the Indianapolis Colts, Mike Vanderjagt (then considered one of the league's top kickers) missed a potential game-tying field goal, and the Steelers killed the clock. Super Bowl XL featured arguably the worst officiating in Super Bowl history, with two penalties nullifying both a Seattle Seahawks touchdown and a deep pass. The Steelers still only won by 11, and the objectionable calls took away potentially 14 Seahawks points. The following year, the same Steelers team went 8-8 and finished third in the AFC North, ahead of only the Cleveland Browns.
1988 San Francisco 49ers
The San Francisco 49ers were a powerhouse for much of the 80's and early-90's, but the 1988 iteration of the team was actually fairly mediocre. The 49ers went just 10-6, with five of their victories coming by less than a touchdown, setting what was then the record for the worst winning percentage for a Super Bowl champion (eventually tied by the 2007 and 2011 New York Giants). Another mind-boggling statistic to come out of this season was that the 49ers leading receiver was halfback Roger Craig, despite the team featuring Jerry Rice. In Super Bowl XXIII, the 49ers faced the Cincinnati Bengals in a rematch of Super Bowl XVI. The Bengals entered the game with a superior record at 12-4, and the 49ers needed a 92-yard drive with under three minutes remaining to get by their rivals. The game ended with a 20-16 Niners victory, one of only two Super Bowls in the 80's decided by less than a touchdown. The other? Super Bowl XVI, between the Bengals and the 49ers.
1968 New York Jets
The 1968 New York Jets are one of the most celebrated Super Bowl champions in NFL history. Their Super Bowl III victory led to the NFL-AFL merger of 1969, and has been dubbed by some the most important game in football history. None of this changes the fact that the '68 Jets were not a phenomenal team. Joe Namath completed less than 50% of his passes that season and threw two more interceptions than touchdowns. The Jets barely defeated the Oakland Raiders in the AFL Championship, and two teams (the Raiders and Chiefs) posted better records than they did. All this in a league that, in retrospect, was worthy of much of the criticism it received. The AFL was simply not on par with the NFL, a league where only two seasons earlier the Colts had won 11 of 14 games and failed to reach the playoffs. But apparently no one told any of this to the Baltimore Colts, who played an abysmal game. Colts Quarterback Earl Morrall, who had led the NFL in passer rating, completed only 6 of 17 passes and threw three interceptions, eventually being benched for the then-ancient Johnny Unitas. To further muddy the water, some Colts later alleged that Morrall had been bribed to throw the game, a claim that has never been proven.
2007 New York Giants
The 2007 New York Giants went 10-6 in the regular season, finishing second in the NFC East to the Dallas Cowboys. Osi Umenyiora was the team's only starting Pro Bowler and the Giants trailed in every postseason game they played. They may have entered into NFL lore by knocking off the 18-0 New England Patriots, but if not for two consecutive dropped interceptions by Asante Samuel and the supremely over-confident Patriots playing what was by far the worst game of their season, the 2007 Giants may be remembered as one of the worst teams ever to appear in a Super Bowl, much less win one. The 2008 Giants were a much improved team, starting the season 11-1 before losing four of their last five and being eliminated in the Divisional Playoff.
2012 Baltimore Ravens
The 2012 Baltimore Ravens finished 10-6, beating out the Cincinnati Bengals as AFC North champions by virtue of the third tiebreaker. Six of their ten victories came by three points or fewer, and they lost four of their last five games. In the AFC Wild Card round, the Ravens handled the Indianapolis Colts (who had gone 1-15 the year before), but they needed double overtime and a patented Peyton Manning choke to get by the Denver Broncos in the Divisional Round. In Super Bowl XLVII, the Ravens took a 28-6 lead before a spontaneous power outage suspended play for 34 minutes. When the lights came back on, so did the 49ers, who eventually cut the lead to 34-29 and drove the ball to the Baltimore 7 yard line by the two-minute warning. The Niners eventually turned it over on downs, with a controversial no-call on a potential pass interference sparing the Ravens an almost-certain loss. The Ravens took an intentional safety to preserve the 34-31 victory. The defending champions were decimated by players leaving in free agency and retirements during the ensuing offseason.
1970 Baltimore Colts
The 1970 Baltimore Colts finished their season with an 11-2-1 record, with 7 of those wins coming by a touchdown or less. To their credit, the Colts performed well in the playoffs, beating the Cincinnati Bengals 17-0 in the Divisional Round and the Oakland Raiders 27-17 in the first-ever AFC Championship Game. In Super Bowl V, the Colts met the Dallas Cowboys, who had posted a 10-4 record in the cutthroat NFC, with 8 of their wins coming by 10 points or more. Super Bowl V is generally regarded as the worst-played Super Bowl in NFL history, often referred to as "The Blunder Bowl." The Colts and the Cowboys combined for 11 turnovers. After holding a 13-6 lead for the majority of the second half, Cowboys Quarterback Craig Morton threw 3 interceptions in the fourth quarter, leading to 10 Colts points and granting them a 16-13 win. The Colts performance was so uninspired that the Most Valuable Player award was given to Chuck Howley, a linebacker for the opposing team. Howley remains the only player on a losing team to be named Super Bowl MVP.
1980 Oakland Raiders
Early in the 1980 season, few expected the Oakland Raiders to make the playoffs. They had gone 2-3 in their first five games before putting in a 33-year-old Jim Plunkett at Quarterback. After Plunkett took command, the Raiders ripped off six straight wins, won nine of their final eleven, and finished the season 11-5. Still, the Raiders finished second in the AFC West to the San Diego Chargers, and barely squeaked in as a Wild Card. After breezing by the Houston Oilers in the Wild Card round, the Raiders flirted with elimination in the Divisional Round against the Cleveland Browns. Trailing 14-12 with less than a minute remaining in the game, the Browns had the ball on the Raiders 13-yard line and were in position for a potential game-winning field goal. The Browns called a pass play, "Red Right 88" and quarterback Brian Sipe forced a pass to tight end Ozzie Newsome. The pass was intercepted in the end zone by safety Mike Davis, securing a miracle victory for the Raiders. In the AFC Championship the Raiders met the Chargers, hopping out to a 28-14 lead by half time. The Chargers rallied back, cutting the lead to 28-24, before Oakland extended the lead to 34-24. The Chargers responded with a lengthy drive that culminated in a field goal. The Raiders' defense told the offense that they were exhausted and would be incapable of stopping the Chargers if they got the ball again. The offense rose to the occasion, holding onto the ball for the final 6 minutes and 43 seconds of the game. In Super Bowl XV, Philadelphia Eagles quarterback Ron Jaworski threw three interceptions and the Raiders cruised to a 27-10 victory. The following year, the Raiders went 7-9, finished 4th in the AFC West, failed to reach the playoffs, and left Oakland for Los Angeles.
1974 Pittsburgh Steelers
1974 marked the beginning of the Pittsburgh Steelers dynasty, but it was not a particularly impressive road to the top. The Steelers posted a decent 10-3-1 record, but first-time starting quarterback Terry Bradshaw completed just 67 passes for 785 yards, including seven touchdowns and eight interceptions. The Steelers trailed in both the Divisional Round and the AFC Championship, before downing the Minnesota Vikings in Super Bowl IX by a score of 16-6. The '74 Steelers road their phenomenal defense to the title, and while there is nothing inherently wrong with this formula, it doesn't necessarily make for one of the all-time great championship teams.
2011 New York Giants
The 2011 New York Giants finished the regular season with a sorry 9-7 record, reaching the playoffs by virtue of playing in the then-weak NFC East. To make matters worse, five of their wins came by five points or less and five of their losses came by double-digits. In the NFC Championship, 49ers wide receiver Kyle Williams fumbled on an end around and muffed two punts, gifting the Giants 17 of their 20 points - and the Giants still needed overtime to get by the 49ers. In Super Bowl XLVI Tom Brady missed a wide-open Wes Welker, who saw the ball glance off his fingertips on a potential clock-killing drive by the New England Patriots. Eli Manning then completed a deep pass by virtue of a tremendous sideline grab by receiver Mario Manningham. Leading 17-15, Patriots' head coach Bill Belichick elected to allow New York to score, and Ahmad Bradshaw (fittingly) stumbled backside-first into the endzone for the game winning touchdown. The largely unchanged 2012 team posted the same record and failed to reach the playoffs.