I personally thought Costa was going to KO Izzy because of the size/power difference
But during the fight, to my eye it seemed like Izzy's punches were actually faster and more powerful
Both have really high KO% but it's crazy how not too long ago Adesanya was considered pillow-fisted
Of course it is possble. Punching power comes from transferring power from the legs, hips, core, torso to the arm.
What you can bench press and how you look means almost nothing to punching power. Being muscle-bound is, in fact, an impediment to that transfer of energy.
But, even more importantly, how hard you punch is much less important than how accurate you are. If I only need to touch you with pinpoint accuracy on the chin with enough force to break a board to knock you out, then who cares if the other guy's punch can break through five cinder blocks, but he can't deliver that anywhere that is going to put me out?
Adesanya was never considered "pillow-fisted" - not sure where that came from. He doesn't force the KO, but he has fifteen stoppages out of 20 wins, all via strikes.
Tommy Hearns was a devastating power puncher when he was a welterweight. This is what he looked like when he was knocking everyone out in that weight class -