Most fighters can fight with out a corner, but to get some were in the POLTICS of boxing, a good Corner is almost needed. Ali would never had gotting a shot as early as he did with out the backing he had. Same goes for Louis, he would have been like Harry Wills. Jack Johnson's Corner mostly out bid other foes for the shot vs Burns. I dont think Johnson would have goting the shot on his own. Marciano can fight, but regardless, he would never had a shot with out the smooth Al Wile. The list goes on, yeah there are expecteds to evey rule. But most cases it applies here.
Easy 1. Jack Johnson 2. Muhammad Ali 3. Floyd Mayweather I believe each of these three fighters would have attained glory no matter which trainer they had. Jack Johnson in my opinion is on a tier of his own however. After reading as much info on him as I can, if someone asked me who his trainer was, I wouldn't have an answer for them. That man was probably teaching all of his "trainers" more about boxing than they knew themselves!
Again, non of these guys got to the top on there own, they had guys that talk them into the title shots. Louis with the purse with Braddock. Johnson's manager out bidded Langford's manager for the title shot. Again, yes they can fight with out them, but it was the corner that made sure the fights were made. And money on the table for it to happen.
Harry Greb, James Toney,B-Hop,Calzage,Archie Moore,George Foreman2,Joey Maxim,Bennie Briscoe,Carlos Monzon
Archie Moore was going NO were fast until he hook up with Jack Doc Kearns, who had the right connections to get Archie Moore the lightheavyweight championship title shot. Had the hook up not happen, Moore would have been the Charley Burley of his era. Same with Maxim, Kearns made the fights for Joey to be champ.
I thought the question was that they could navigate inside the ring at a certain point in time without the corner. Management is another issue indeed, even Ali and Leonard without Dundee would have not been the same Dundee helped vs Liston and Cooper, Frazier and he helped Leonard vs Duran 2 and Hagler with inside and outside the ring advise. I dont think anyone really made it with out some string-pullers
Without Dundee Ali would have quit on his stool against Liston when he had that substance, whatever it was in his eyes.
If thats the question Tyson would be a good example. His team after Spinks was a joke. After prison leading up the second Holyfield fight it was worse.