Let's start from early in his career to answer your question. I will do it in bullet points so as to make it easy for you understand.
>Martinez started boxing when he was 20 years.
>Whilst he was winning world titles he was also working 2, sometimes 3 other jobs.
>His only real loss came to Margarito 12 years ago. He hasn't really lost since. Most of his early wins came whilst working at least 4 other jobs.
>He dominated Kermit Cintron at 154 and TKO him but the fight was resumed after a 10 minute break because he claimed it was a head butt.
>He knocked out cold one of the most avoided fighters in the history of boxing, Paul Williams. Williams had never been knocked out before. He had also honestly won the first fight.
>He disfigured Kelly Pavlik's face. Made him look average at best.
>He knocked down Dzinziruk 5 times in 8 rounds. Dzinziruk had never been knocked down or knocked out before. As Jim Lampley stated "It is impossible to look good against Dzinziruk. Martinez looked sensational."
>Darren Barker had never lost before. Martinez knocked him out.
>Dominated/Schooled Chavez Jr who was without a doubt 25+ pounds heavier than him on fight night. Technically a Cruiserweight. That is the equivalent of Mayweather fighting an Andre Ward if not heavier fighter.
>Got knocked down by this guy who was 25+ pounds heavier and came back punching. Not clinching, but punching.
Need I say more?