Okay let's have some fun now, this question has many foes to question. Was it Margarito? Was it Mosley? Perhaps Mayweather? Any way I swear I could remember Pacquiao saying Cotto was his hardest fight because "after 6 rounds they still were even." This comes after what? 2 knockdowns on Cotto if I remember co4rectly and a stoppage in the 12th? PAC also had a swollen ear/ cauliflower/ busted eardrum. Whether it is or not, Miguel praised him (Manny) of being the best fighter in the world. Which stems another question 1 a) how many fighters confessed with their own mouth that he pacman, was the pound for pound king. Me thinks: Mosley, Cotto, I can't recall many others. You be the one to decide:
Agapito Sanchez a dirty foul filled fight in which Pacquiao was considerably uncomfortable in. Nedal Hussein floored Pacquiao badly hurting him. Oscar Larios shook up Pacquiao pretty badly in the 3rd round of their fight. And then obviously you have 1st Morales fight, Marquez fights.
Hardest is a term open to interpretation. I'm going to go with his first fight Against JM Marquez. Manny knocks down Marquez three time in the first round and only ends up with a draw.
Morales 1 Morales went toe to toe and was better that night than anything Pacquiao had to offer. Cut him up, outlanded, and outworked him and even had the nerve to switch southpaw in the final 2 minutes of the fight as to prove a point that he was better. Had Manny and Buboy Fernandes cry in Buboy’s arms after the decision was read out also. I have never seen him that defeated after that fight. Infact I believe that’s the fight he needed to become the all time great that he now is. Similar to Floyd vs Canelo
That's my choice too, Manny was simply up against a better fighter that night. What he usually did just wasn't enough and that along with the draw with Marquez forced Manny to retool and evolve into the fighter that would go on to have one of the best runs ever seen. As for Morales that really was his last great performance. His career really U turned after that fight, losing to Raheem then the 2 rematches with an improved Manny and then Diaz. But yeah that win over Manny sealed his legacy regardless of what happened afterwards.
Two fighters that geniunely troubled and gave Pac all he can handle was Marquez and Morales.In terms of punishment. I would say Cotto he was in fetal position in hospital. The rest meh! Void ran around and never really respected that kind of spirit.
Obviously you have to include Agapito on the list of course. But fouls are not included in boxing. Hussein landed a lucky shot and got an unlucky count. Larios shook up Pac. But got ping ponged around the ring for the remainder of the contest. The Morales and Marquez was realness. As they destroyed him without fouling and no lucky shot just pure skills, heart and many other amazing qualities. No running cough ( VOID) and mano o mano slug.
He beat Margarito and said "**** this, I am never going to fight at 154 again". It probably was his hardest fight physically.