Duran deserves a mention. Well, actually he probably doesn't belong in this category, but Moran does. For even though he briefly held the bantamweight title, Owen very likely could have been featherweight and lightweight champion, and reigned for quite a while.
Josiah F. Jenkins. He could have been the greatest fighter of all time and made millions of dollars, but never got interested in boxing and spent the rest of his life in a low-paying assembly line job instead.
*Easy... Cotto is the unluckiest.. it's very likely that both his brutal loses were to two guys who cheated.
BERT GILROY was actually called "the unluckiest champion that ever was!" by International referee Eugene Henderson from the late 1940s onward, because of the war and British Boxing politics. A world champion prospect from 1938 - 1945/46. http://cyberboxingzone.com/boxing/0001-delisa.html
Hector Thompson - IMO the greatest fighter ever to come out of Australia. But very unlucky during his career. 1) Both Roko Spanja and Chuck Wilburn died from injuries sustained in their respective bouts with Thompson. 2) When nearing his justifiable title shot in his prime in '74 he was forced to retire on his stool against clubfighter Javier Ayala with knee damage, thus setting him back with an operation. 3) Received 2 title shots during his career, unfortuanately the two fighters in the other corner were named Duran and Cervantes.