thats what they call 'heavy hands'. if youve sparred with a guy who has them, you know. they can hurt you on accident with a normal looking punch, even a jab. if they dont rock you, they bruise you or cut you up.
this isnt describing guys like rumble or ngannou who explode into their punches, their power comes from their entire body. it describes guys like volkan and stipe who hit you very hard with a pedestrian punch. no one really knows what it feels like except the guy on the receiving end. cant really teach it, either.