Paulie Malignaggi was definitely an overachiever. To be fair, he did have some boxing skills and ability. He was pretty agile, and had good footwork. He had good distance control and an excellent jab from his waist. But he was very extremely limited in his skillset, and he had absolutely no power whatsoever. Really good boxers can get away with subpar power at a world class level, but usually not a deficient to that extent.Plus, his defense was almost entirely dependent on his footwork. But he found a way to make a genuine career out of the sweet science. Sure, he lost most of the big fights he had, but he still beat Juan Diaz, N'dou, Judah, and Senchenko. That's not a bad for guy with pretty limited talent.
Vito Antuofermo - A club-footed bleeder, with short arms, only 5' 7" for a middle, no punching power, despite this went on to become champion and fought the great Hagler to a draw. A fight I thought he won. Sergio Martinez Rocky Marciano
I vote Bazooka Limon. You'd watch him and wonder how in the world he went so far with no great athletic skill, looping soft-looking punches and slow feet. Then you'd realize how far heart and toughness can take someone. I was always amazed by Craig Bodzianowski fighting so well with a prosthetic leg. Just incredible to consider seriously.
Limon was going to be my answer. Broke literally every rule in the book and still succeeded at a world level in a absolute shark pool of talent.
Anyone mention the Toy Tiger, Art Hafey? A small, 5'2 featherweight with a crippling muscle ailment who's now regarded as one of the better fighters to never get a title shot.