Re: I thought punching power could not be improved at all!
I don't think Marquez was a harder puncher. He was clearly looking for a knockout though, contrary to the other 3 fights. He was sitting down on every shot and throwing each one with the intention of laying Pac cold.
The KO blow was a combination of Juan throwing the perfect punch and Pac lunging into the shot face first.
The first knockdown was a haymaker that Juan set up perfectly and it caught Pac at a weird angle that he couldn't see. It'd have been more surprising if Pac didn't go down from that shot.
Marquez throwing with more conviction than ever against Pac + Pac fighting recklessly = Pac getting KTFO by Marquez.