When a boxer loses but still excels in a different way. Best examples I can think of are Muhammad Ali's loss to Joe Frazier,Frazier's loss in turn,to Ali,and Sugar Ray Leonard losing to Roberto Duran. Thay all displayed remarkable tenacity and guts.
Ray Mancini vs. Arguello usually gets mentioned Meldrick Taylor vs. J. C. Chavez I Wepner, Cooper, Bugner were all elevated by fighting Ali Oscar Bonavena vs. Frazier both times out Duran vs. Hagler (though I've had him winning)
Jimmy Young vs Muhammad Ali Floyd Patterson vs Jerry Quarry II Floyd Patterson vs Jimmy Ellis John Conteh vs Matthew Saad Muhammad I
Get with the program. On ESB, Duran never lost except when he didn't want to win or was old, or green, or unfocused, or because his opponent made funny faces.