He's just too damn strong physically. For 5'10 160lbs he bulldozes everyone that stands in front of him and has them retreating backwards. You can tell by his physique with the barrel chest and wide back, he looks like a weight lifter or pro wrestler from the 1930s. Old school muscle. I bet if a regular guy tried to shoulder check him they would bounce off his shoulders like rubber.
Look at the resume of the men he has fought, and you can see why they get KTFO. Lemieux is his biggest win, and he himself got KTFO by a journeyman former Jr. MW titlist with a dozen losses or so.
Fun fact. Golovkin used to be a wrestler. I imagine Soviet schools incorporate a lot of old school techniques.
I think if you measured his power on a punching machine he would't be so much above other MWs as one may assume. IMO, his knockouts are mainly the result of good distance control and a phenomenal punch placement that allows him to maximize the power he has. I think both Macklin and Murrey both said that he had solid power but it was more the punch placement and constant pressure that troubled them the most.
I have always noticed he could penetrate all kinds of defense. Even against opponent who have noticeable reach and speed advantage, ggg always seems to recognize the contact distance, make quick decision and land first. Against speedster or boxers, he has nack of punishing an escape move to the body without worry of counters. He has some unique punches and combinations like the jab and uppercut that surprises.
What barrel chest? Seriously, it is called ring IQ and applied intelligence. His distance, timing and balance and amazing.
He has much better speed than given credit for, his unparalleled technique and timing is what makes his decent speed seem like unbelievable speed and pressure, from his opponents eyes to their mouths after being terrorized
I find it amazing he's Never been down as a ams or a pro that's impressive especially considering he's approaching 400 fights GGG's ams record was 345-5