paul ingle - remember being pissed off when it was announced he was fighting naz. just thought he was strictly domestic level cannon fodder. despite his excellent effort i didn't think he'd win a world title. he did and defended it in MSG. :yep just so sad how it all ended up. :-(
Fabio Wardley has to be a shout, he was written off at every level, no one expected him to win the British title never mind the world title.
Outside of the ones mentioned....maybe Ricky Burns. Lost comfortably to Alex Arthur and Carl Johansson early in his career without really doing much previous to that. Johnny Nelson. Lost his first 3 fights. Got to be some kind of record. Losing the first 3 and still going on to become a World champion.
My first thought was Johnny Nelson, lost his first 3 and 5 of his first 11 fights, so after 11 fights he had an almost 50% loss rate.