Deciding the biggest upset in Super Bowl history usually centers on historic matchups where massive point spreads were completely upended by disciplined underdogs executing flawless game plans. One of the most monumental upsets occurred in Super Bowl III, where Joe Namath and the New York Jets of the American Football League defeated the heavily favored Baltimore Colts of the NFL—who were laying nearly 20 points—in a stunning victory that legitimized the AFL before the full league merger. Another iconic shocker took place in Super Bowl XLII, when the New York Giants derailed the New England Patriots' quest for a historic undefeated 19-0 season by handing them a stunning 17-14 defeat as 12-point underdogs, sealed by legendary plays like David Tyree's helmet catch. Additionally, Super Bowl XXXVI featured the heavily underdog New England Patriots, led by a young Tom Brady making his first postseason run, defeating the explosive St. Louis Rams' Greatest Show on Turf as 14-point underdogs. Each of these games redefined professional football history by proving that regular-season dominance and heavy betting odds guarantee nothing once the ball kicks off.