Cotto. Calzaghe didn't beat a reigning champ until he was 34. He made up for lost time in a hurry though
Your question is flawed in itself.. NOBODY , not that I recall, makes a career out of winning vacant titles. They may have won 'em but that doesn't mean their entire careers revolve around those titles, especially nowadays when titles don't have the same value due to so many "available". Fighters make a career out of hard training, and consequently winning good, exciting fights . If they don't win , they don't get a payday, they don't make a career.
Well, Cotto has been in the game for like 8 years and all three of his belts were vacant when he won them. He has never even faced a reigning champ. Top Rank paid step aside money so that he could fight Quintana for a vacant belt and then they pounced on the opportunity to fight Jennings for that WBO belt that Williams vacated(Top Rank made no efforts to match Cotto with Williams when Williams had the belt). That's about as close as you can get to making a career out of winning vacant belts.
That's not true, Fraudarinelli only held the WBO title and that belt was handed to him without having to fight for it when Johnny Nelson retired.