Tommy's punch would have KO'd Pac. Not sure if JMM's punch would have KO'd Duran. (I do realize the weight difference, but still) Also, this was a fight between the two best fighters in the world at that weight. And as stated before, Duran had never been pulvarized before that, and it never happened since.
Duran - Hearns is similar to the Pacquiao-Marquez knockout but at an ATG level, plus nobody before that or afterwards was able to put Roberto's lights out like that.
Well I don't think the punch that Pac took would have dropped Duran, for starters much less have KO'd him. If you watch the Moore or the Barkley fight he was hit with far harder punches than Pac was. That said, we all know it's the punch you don't see that causes the most damage. But even when Hearns landed flush and dropped Duran, he was on his feet not long after the fight was stopped. Can't say the same about Pac. Anyway, Marquez's punch was certainly more devastating in terms of damage to a fighter, but in terms of who's punch was harder, clearly Hearns was. So I'm not sure how you answer this question. As many have pointed out Duran was never poleaxed like that either before or after in his career, and the way Pac was dropped makes me think that if Hearns had landed that punch against him he might very well have suffered a permanent injury.
Hearns Duran. Nobody treated Duran like that. Manny P has been ko'd before so that was nothing new. Duran had never been treated like that-ever.
JMM/Pac are 2 ATG's that fight around the same weight. A past Prime JMM beat a closer to prime Pac. Hearns, on the other hand, was naturally bigger than Duran(by at least 2 div) and fought a past-prime Duran while Hearns was at his peak. I've always wondered why nobody ever mentions the size disparity between Duran/Hearns.