You need to fight the Lizardman 'Gunter' as Rolf. Or at least that's how I did it. The order of whom you fight is random, and if you reset the game it will never change, but if you get beaten and then restart when asked the game reshuffles the match order. Keep doing this until you are fighting Gunter first.
Here's how I double perfected him a couple times. Walk forward, spam A, walk forward, spam A, etc. he doesn't defend, he really doesn't, it's awesome!