Well the fight was at junior middleweight, Duran came in badly weight drained his own fault of course, however for a fair comparison Monzon would have to go up to cruiserweight and face a fighter around 6'5 or 6'6, that never happened.
Monzon could have went up to 175 if he really wanted it but there was a killer called Bob Foster lurking in those waters. A hypothetical natural middleweight Duran most definitely goes to 175 to test himself (and Bob) in Bob’s natural habitat. Duran was just a natural badass. Monzon imo was in cricket parlance a “flat track bully”. He liked the odds on his side. Simply put I’m not a massive fan.
He came in badly weight too much times (Hearns, Leonard, Hagler) to be considered more badass than Monzon according to your argument. The truth is Monzon had stone hands, granite chin and formidable stamina. Duran, unfortunately, only stone hands. For this I strongly think if Monzon had wanted he would have dominated both in the LW and in the cruisers.
Yes he didnt always prepare for some fights, however he was a NATURAL LIGHTWEIGHT 135 lbs. and was nearly unbeatable at that weight. People forget Duran was always the smaller, older man in the Four Kings. Duran was more dominant at Lightweight than Monzon was at middleweight and then he moved up and won 3 more titles. We can say we "strongly think" that Monzon could have moved up and dominated at heavier weights, the fact is HE NEVER DID. And if Duran had only had Stone Hands we wouldn't have achieved near what he actually did.
However like someone said here he was shot by his first wife but he didnt die. Its enough this to understand who Monzon was.
Duran dominated in multiple divisions and was a far better boxer. Monzon feasted on blown up welters past their prime and usually had a size advantage in the one division he competed in. He was also an abuser of women. Coward.