Julian Jackson was arguably P4P the hardest puncher of all time. Marvin Hagler had arguably the best chin of all time. What happens when an immovable object meets an irresistible force? Say Jackson lands a bomb of a right hand on Hagler's chin. Could he knock him out?
Julian Jackson could KO a horse so it's entirely plausible that given Hagler's chin to aim at without any obstacle, he could floor him. But Hagler could box and had the strength to hold Jackson off so when it comes to the art of boxing, Hagler was several leagues above Jackson. So, yeah, Jackson could KO Hagler, but I don't think he'd likely be able to.
Hypothetically, if he landed the perfect punch, Hagler doesn’t see it coming, walks into it, chin up in the air, then yeah I can maybe see Hagler taking a 10 count. Hagler had an ATG chin, but was still human, and this is Jackson we’re talking about. People always bring up Hearns, but Hagler smartly closed the distance so Hearns couldn’t get full extension and leverage on his right hand like he did versus Cuevas, Duran & Shuler. The shot that briefly stunned Hagler was a short uppercut inside followed by a looping overhand right. That’s not to say Hearns would have KO’d Hagler if he did land his ideal punch though. Hart hurt Hagler more than Tommy did. The chances of Jackson landing that one perfect shot are so slim. Hagler would most likely outbox Jackson and break him down and stop him in the mid rounds.
If Hagler just stood their and took the shot cleanly from Jackson I'm sure Jackson could knock him out. But in a actual fight, his chances would be slim to none. It would be Jackson being assisted off the floor within 5rds.
