Carlos Monzon and Marvin Hagler are pretty dead even but I would give Monzon the edge because;
a. Monzon had 1 more title defense as undisputed, which is pretty insignificant.
b. Monzon beat the great welterweight who went up in his time, while Hagler lost a split decision to a very inactive great welterweight.
c. Hagler struggled with most of Monzons leftovers in the end of the day.
Marvin Hagler
Harry Greb
Won 262 fights and lost only 20
Defeated 18 World Champions and 11 Hall of Famers
Defeated over 40 heavyweights and many of them high ranked contenders
Only man to defeat Tunney and handled Dempsey in all out sparring sessions. Dempsey refused to give him a title shot.
Loved Robinson perhaps the most gifted fighter of all time whom I rank #2 all time behind Greb. Monzon and Hagler were beasts but Greb had the best resume of all of them and in fact anybody hands down and would have beaten any of these guys at his best. He was fearless and he was fast and mean too!
Based on historical records ,Greb is the greatest fighter that the succeeding generations of boxing fans never saw on film. At least we still have some preserved videos of Hall of Famers and ATGs Gene Tunney, Tiger Flowers, Mickey Walker, Tommy Loughran and we saw and are still seeing how good to great they had been in their days---and Greb fought them in series and acquitted himself very well in victories and defeats. Greb also fought not just middleweights but light heavyweights and heavyweights and like Walker distinguished himself against the bigger, stronger foes back in the days when boxing was more of a manly/gentlemanly art of creating mayhem than science.And what makes his feat more admirable was that he already was suffering from impaired vision when he hit his prime.
The only reasons Greb is not compared well with the acknowledged greatest middleweight and arguably the GOAT Sugar Ray Robinson are that there was not much by way of documentary video, especially films of him in action when modern boxing chronicling started years after his death and that he lost some fights on his way up.
Personally, I consider, Greb as a class of his own at middleweights.
Greb most definitely had far better resume than both Monzon and Hagler who fought exclusively at middleweight during their prime and career.
Marvin Hagler had it all. This includes an Iron chin that not many boxers had. By the way, Hagler beat SRL! That was bogas and a true injustice of the sport but then again it is boxing.
Greb had more fights and fought at different weights, so he was more versatile than Monzon or Halger.
Monzon had several draws and would not travel to defend his title.
I think those two things make him slightly less than Halger in my rankings.
Marvin Hagler was one bad mutha,
