Keep the difficulty on Medium and the KO counter on 1, then select Mama Tua.

Use her forward, forward+ High Right punch (up C/Triangle/X Button). The reason you want put it on that difficulty is because the Championship match triggers a fight with J.R. Flurry on Medium, Mama Tua on Easy, and Joey T on Hard difficulty.

If the opponent is low on health, press down+forward+High Right Punch