Obviously, when you are rating a great fighters chin, you have to look at their overall career.
SRL is a strange one for me, because as a Welterweight, he had a awesome chin. I can only remember Duran wobbling him briefly in the first fight & that's it. He took some mind numbing punches from Hearns & never looked like buckling, yet later in his career, he tasted the canvass numerous times. To his credit, he always got up & fought back, with the Camacho fight being the exception, when he was nearly 41 & should not have been anywhere near a boxing ring as a pro fighter.