We have done the fighters ruined by a defeat, but who are those who's career ultimately benefited from a defeat(s)? A few to start things off: Simon Brown rebounded strong after his early career defeat to Marlon Starling. Barry McGuigan claimed the Peter Eubank defeat early on gave his career a focus. Marvelous Marvin benefited from a tough run of fights in the mid/late 70s, that included him being on the wrong end of a couple of decisions.
Bernard Hopkins vs Clinton Mitchell (inspired Hopkins to come in better shape and drop a weight class) John Ruiz vs David Tua (made Ruiz relearn fundamentals and polish boxing ability) Anthony Joshua vs Andy Ruiz (ditto to the one above) Rocky Marciano vs Henry Lester (started Rocky's unwavering commitment to coming in at the pinnacle of fitness and cardio for every fight) Jack Johnson vs Joe Choynski (While both were in prison for illegally prizefighting Choysnki taught Johnson many tricks and tactics which benefitted Johnson, he also frequently sparred with Johnson)
Leonard vs Duran 1. Took an excellent champion to an ATG one. Louis vs Schmeling. Polished himself off from defeat, fixed his Fundamental flaw and became one of the greatest fighters ever. Those were the first 2 to come to my head.
I am not sure it was due to defeat or just needing more experience all together, but I would say Azumah Nelson. Regrouped from Sanchez won the FW title within 2 years, held it for 3 before moving up to SFW for another 2 years. He would have 8 years before his next loss and that was at LW to Sweet Pea where he did not look good at the weight at all and moved back down!
The one that stands out most is Nigel Benn against Michael Watson in the 'Supertent' at Finsbury Park. Benn was 22-0 with 22 KOs (95% in 2 rounds or less) and punched Watson's guard for 6 rounds before being put over by a jab, exhausted. Moved to America to rebuild himself, learn to pace himself and have a scintillating career.
Jimmy McLarnin took a real thumping from Sammy Mandell, Ray Miller and Billy Petrolle, but once he gained a bit of experience, he gave the three of them a good licking in their returns. Also, a young Ezzard Charles took a hammering from Lloyd Marshall and Jimmy Bivins. He then went in the army and came out a bigger and better fighter and gave the two sweet revenge.
Duran vs. DeJesus. Got dropped with that left hook and lost the first go. Got dropped (again in the first round) second time around but overcame by sheer ferocity. Ray Arcel told him for the third fight if he wanted to go out and fight the same way that hook would be waiting for him. So he listened and learned and from that emerged as the brilliant boxer-puncher who was able to adapt and use all of his tools to become a champ all the way up to 160.
Not sure how everyone missed Ali, he was an untested HW from the 60’s who fought Frazier...and Frazier humiliated him big time. But give Ali credit, he was able to rebound and have the best years of his career in the 70’s thanks to the humble pie Frazier served up that night!
Bobby Czyz after being mauled by Hamsho realised it was petty trying to make MW anymore as his camp had being giving him water pills to help make weight. Moved up to LHW and a much stronger fighter and became world champ.
Chiquita Gonzalez was regarded as a pure banger and showed it against Michael Carbajal, dropping him twice, but ended up getting KO'd himself in 7. In the two subsequent rematches he turned pure boxer and Carbajal couldn't do a thing with him and Chiquita walked away with two 12 round decisions.
I think Canelo took a lot from the Mayweather loss - he became much more defensively sound. Benn v Watson David Haye v Carl Thompson - 10 or so fights into Haye's career in which he had been blowing people away, Haye gassed vs Thompson and was taken out. After that he made sure he always trained like a demon in camp. Funnily enough, although he did reach the top, he trained like a mad man and I think that culminated in a lot of his injuries. Ricky Burns v Carl Johanneson - Ricky lost this for the British title but then went on a 6-7 year winning streak picking up a world title before losing to Terence Crawford.
Reggie Strickland! He learned that if he was the go-to-lose-guy he could make money by actually losing. https://trendcelebsnow.com/reggie-strickland-net-worth/ His low estimate worth believe it or not is around $1 million dollars. Record of 66-276-17