Some zombies are talking about how Ishii flopped and cant take a punch, calling him a CAN.
More knowledgable people would know that the combo Fedor did would most likely knock out anyone. That punch behind the ears tapped the sweet spot.
First punch was a straight to the face that smashed Ishii's nose, second was an uppercut that jolted his head up, third punch was the killer that was basically a KO punch that ****s up your equilibrium (the sweet spot).
Fedor's punch directed sweetly and powerfully, we all know how powerful Fedor's power punches are. Even less powerfull fighters an get a KO if they land at the sweet spot.