Leonard was a class act. Extraordinary speed, intuition and over-all skills.
As far as the Hagler bout I say Leonard handled him like a true craftsman. I believe that he had Hagler very tentative to let his puches go once Hagler saw how outclassed he was in speed, he was simply worried that Leonard would make him look bad. With Marvins extremely high sense of pride he was tentative through the whole bout and never did really let his hands go fluidly. Leonard won that fight.
Leonard displayed legendary skills that night against Duran. I am certain that with Durans enormous bravado he would much rather get ko'd than to be infront of millions of fans being made to look the fool. Leonard knew this, played his showmanship and took Durans heart. There is no victory more fulfilling in the ring to a fighter than to take your opponents heart and grind it into submission.
Leonard could display every skill of any great fighter through history, except for one aspect. He never had that true one punch ko power that feeds every boxing fans craving. He could certainly ko people but I believe that his ko's came from great timing, placement and the speed at which they were delivered 'shocking' many opponents to the cavas.
Overall Leonard is easily within the peramiters of an All-Time Great............Rockin'