Determination for sure. Also one of the strongest chins in the history of the division. Never knocked down (w/due respect to Roldan), seldom if ever hurt.
His granite mother****ing chin, one of the greatest of all time. His determination (as so many posters have mentioned here) is a close second.
Probably his versatility and length. Halger did many thinks well, but few things on the elite level, aside from taking a good punch. Halger's ring IQ and issues with faster fighter to me were the flaws in his game. Could have been a little better on defense as well.
Yeah, I think what was most central to Hagler's success was that he had such excellent fundamentals and the physical talent to use them successfully. He knew how to move and how to throw every punch in the book while controlling his weight and keeping his balance, and there really aren't many boxers his size or bigger who could string together so many hard, fast punches so consistently. That's what stands out to me when I watch him during his absolute prime (maybe eearly 80 - early 83ish). I know that Hagler's mystique is based around him being a tough, determined warrior but I think all of those intangibles are really secondary.
MENTAL TOUGHNESS! PHYSICAL TOUGHNESS! KILLER INSTINCT! "WAR" MENTALITY! My second favorite fighter, MARVIN HAGLER
He was one of the best ever at his weight, if not the best Middleweight of his generation. He ruled the division when l got into boxing. He beat my home town favourite, Tony Sibson ! Sibbo said at the time & still does, ‘He’s the greatest !’ He had it all. Strength, stamina, great jab, an aura of invincibility, durability, a will to dominate all comers. To pick one is very difficult. He was just Marvelous.