Consistently struggled with a certain style, type of fighter or who could not deal at all with a certain characteristic. For example speed or movement, For example trinidad had terribly uncoordinated feet, his legs always wobbled as if he was drunk and he was terrible at dealing with movement. He did jot look great at all vs DLH and Hopkins. Frazier seemed to struggle badly against big bangers. Foreman had trouble with quick boxers who stick & moved in both careers.(as long as the opponent didnt hesitate. Norton hesitated, froze and got destroyed. Holyfield, Morrison, ali, young and schulz did not hesitate and pukled the trigger and then got out.)
If you look through the history of boxing every fighter who actually fought real competition (fighting fighters who are universally seen as good competition ) found a fighter that for whatever the reason gave them hell. But the great ones usually found a way to win.
Vernon Forrest struggled with a wild Mayorga. This was a case of a textbook technician like Forrest being confused by punches that did not come at him from the usual angles/trajectory. Mosley struggled with good technicians who utilized a great jab. Corrales struggled with fundamental sound boxer, e.g., Floyd and Casamayor Pacquiao struggled with fighters who could employ the necessary footwork to keep him in front of them. Pacquiao had a remarkable ability to always have his lead foot well outside the orthodox fighter’s lead foot. Watch his fight with Cotto to see my point. Poor Cotto was practically being beaten up from outside his own left shoulder.
He really didn't have very many fights, period. That's what happens when health issues ravage your body and career. There were plenty of big punchers around the time that Frazier could have fought, but do you really think any of them would have found much success? Mac Foster, Jeff Merrit, Earnie Shavers, who else...