Julio Ceasar Chavez Jr. started out as a skinny volume puncher that could barely crack an egg. Despite hitting the dank instead of training, he had lineal champ Martinez on the verge of being stopped after landing some good shots. He definitely has become a ko/tko threat after a less than stellar start. The juice/PEDs have helped!

Another guy, to a degree, was Arturo Gatti. I remember watching him as a featherweight, and he was a very slick boxer who could punch, but was more boxer than puncher (watch his fight vs Patterson). He fell in love with the crowds admiration/support as well as the thrill of the knockout and turned into a hell of a knockout threat.