Duran retired after the Hearns loss in 1984. Came back in 1986 at 35, went on to win his fourth title against Barkley at 38.
Barrera got stopped by junior jones then lost via UD in the immediate rematch then went onto retire Spent a year away from the sport but couldent shake the love he had for boxing Came back a much more complete fighter and won multiple titles
Foreman is an excellent case study in successful comebacks, as he was able to adapt his style within his new limitations. Less aggressive, more measured and methodical, utilising a cross-armed defence while patiently stalking. Old Foreman developed skills and qualities that the young Foreman didn't have, which was the key to v2.0 being successful. Boxers who fight the same way as they always did as they get older tend to just be inferior versions of their younger selves. Vitali is one of the noteworthy comebacks of recent years, but unlike Foreman I don't think he made significant refinements to his style. I think it was more a case that he was a lot better than his opposition, and continued to be so despite his advancing years. Toney made a successful comeback at cruiser (and heavy to a certain extent) following his mid career nosedive at 175. This probably had more to do with increased motivation and better "preparation" (heh heh) than anything else.