This can cover a wide range of sports, and also a wide type of comeback.
For example, you could have a team that was 3-0 down who win 4-3, a team 20 points behind at Christmas who win the Title, a boxer that comes back after everyone thought him old and beaten, a cricket team that comeback with a sensational last wicket stand (or something).
Basically, name any of the great comebacks you have ever watched and thought "cor, that was almost worth turning the porn off for".