The biggest pointspread ever in Superbowl betting was in Super Bowl XXIX where San Francisco was an 18 point favorite against San Diego. The 49ers won and covered that game against the Superbowl odds by a score of 49-26.
Superbowl odds for some people will say that the line on Super Bowl III between the Indianapolis Colts and New York Jets was up to 20 points. The problem with going back that far in Superbowl betting history is that it is all hearsay. The Colts opened as a 17 point favorite against the Jets in Superbowl odds and there were reports it was up to a 20 point spread before the game. Since there were no sportsbooks back then it is all a matter of what bookie you talked to. The only thing that people remember about that game is that Joe Namath of the Jets guaranteed victory and the Jets upset the favored Colts by a score of 16-7.
There have been a lot of big Superbowl odds in the past. It started right from the beginning as Super Bowl I had the Packers a 17 point favorite against the Chiefs. The Packers easily covered in Superbowl betting in that game, winning 35-10. The Packers were 13 point favorites the next year against Oakland in Superbowl odds and covered again, this time by a score of 33-14. Super Bowl IV had the Vikings a 10 point Superbowl betting favorite against the Chiefs and Minnesota was routed in a huge upset 23-7.
There have been other big favorites in the Super Bowl including Super Bowl XIV when the Pittsburgh Steelers were an 11 point favorite against the Los Angeles Rams. The Steelers just covered the line by a score of 31-19. The Bears were 11 point favorites in Super Bowl XX against the Patriots and won easily 46-10. Super Bowl XXIV saw the San Francisco 49ers a 12 point favorite against Denver and they won 55-10. Super Bowl XXVII had Dallas a 10.5 point favorite against Buffalo and the Cowboys won 30-13. The next four Super Bowls had big favorites. Only the 49ers covered the spread and the Packers lost outright to the Broncos 31-24 in Super Bowl XXXII. The other double digit favorite was the St. Louis Rams who were 14 point favorites against the New England Patriots in Super Bowl XXXVI and they lost 20-17 in Superbowl odds.