The underdog can "usually" win if they try an unusual (but effective) strategy. Karate kid didn't use a dirty trick (actually, the other guy did), he fought in

The underdog can "usually" win if they try an unusual (but effective) strategy. Karate kid didn't use a dirty trick (actually, the other guy did), he fought in a very standard style. The last second of the fight (when he surprised his opponent with his ability to kick with just one leg) may count a bit, but he wouldn't get that far.