You do have to feel for long-time Bronco fans because they have suffered through some of the biggest blowouts in Super Bowl history, with Super Bowl XXIV being the largest margin of victory (San Francisco 55 Denver 10) and Super Bowl XXII just two years prior (Washington 42 Denver 10).
Other Super Bowls that were notable blowouts were Super Bowl XX (Chicago 46 New England 10), Super Bowl XXVII (Dallas 51 Buffalo 17), Super Bowl XVIII (Los Angeles 38 Washington 9), Super Bowl XXXV (Baltimore 34 New York 7), Super Bowl XXXVII (Tampa Bay 48 Oakland 21), and Super Bowl I (Green Bay 35 Kansas City 10).
XX and XXIV were both true demolition jobs as Chicago and San Francisco thoroughly creamed New England and Denver specifically, but I don't consider either to be the worst Super Bowl ever because both were expected to be blowouts with Chicago being favored by 10 and San Francisco by 12 against an over-matched opponent.
If I had to pick the worst Super Bowl ever, I would probably go with XXII, a true embarrassment for the favored Broncos as they allowed Washington to score 42 unanswered, including 35 in the second quarter. Denver was considered a narrow favorite because of relatively even rosters but with the supposed advantage of having John Elway under center instead of Doug Williams. Washington put up a record 602 yards of offense, including 356 in the aforementioned second quarter, and most rushing yards in a game with 280. The rushing yard statistically is great considering the victors were starting an unknown reserve running back named Tommy Smith, who finished with a record 204 rushing yards and two touchdowns.
Yet, the worst played Super Bowl overall was probably Super Bowl V, where the Colts defeated the Cowboys by a 16-13 score. Both teams combined for a record 11 turnovers, with Baltimore putting up a record seven for a winning club. Dallas set a record of their own in committing ten penalties. The game was so bad that the late Colts defensive end Bubba Smith famously refused to wear his Super Bowl ring due to the awful play.
However, XLVIII has to be in the conversation for worst ever. Denver was favored and, again, had the highest scoring offense in league history, and they were completely overwhelmed on that side of the ball, allowing the Seahawks to do whatever they wanted defensively.