I would say Pacquiao has a granite chin. He's been KO'ed 3 times, but 2 of those times were when he was a malnourished kid. He's taken punches from the likes of Matthysse, Thurman, Cotto, and Mosley, and never went down.
Very solid chin. Kod in his prime years by a perfect punch but has took some bombs in the past and been fine. If we went on a scale of modern top fighters chins where Khan is a 1 and Golovkin a 10 then Id put Pacquaio at 8.
It's obviously great but a lot of it has to do with his movement, angles, aggression, and power. That and his strong mental game. He gets hit but only rarely with his opponent's best punch, he's never where they want him to be waiting to receive it.
No probs what so ever with his chin. The greatest fighter of all time has to have a great chin, an that he has !
Lets be honest here Marquez didn't knock out Pacquiao Pacquiao knocked himself out jumping into Marquez's fist
People forget that Marquez took enough steroids to power the entire NFL in fights III and IV. (see my avatar for proof)
So why couldn't anyone from 147 drop him aside from Roidquez? Larios punched harder than Cotto, Thurman, Mosley, Rios, Clottey, and Matthysse?
Pac dropped/hurt every single opponent in the 5 fights where he was VADA-tested. Clenelo was busted by VADA. Floyd and Roidquez ducked VADA.