The greats that were able to walk away and stay away are a small, elite fraternity for sure. The ones that did so after truly proving themselves in their career are members of an even smaller fraternity.
Monzon and Sanchez ( well he didn't really retire but still ) stick out in my mind... also there are guys like Marcel and Mclarning finished his career with a couple great wins.
packey mcFarland, retired at the age of 27 ,in 1915 at the height of his great careerHe was deemed "uncrowened lightweight champ... Jack McAuliffe retired unbeaten in 1987,at his peak...
Jem Mace basicaly retired as world champion when America got to hot to hold him. He fought the odd bout after that but was basicaly retired at world level. Tom Cribb retired at the top of his game after defeating Molineaux.