A guy who fought Jiro Watanbe he was a Korean boxer. Soon Chun Kwon. Just a filthy piece of work a southpaw who was a mugger he liked to boar in and squeeze as many warning as he could get out of a ref. Tough guy but nasty.
Mike Tyson, Andrew Golota, and Tony Galento come to mind. Tough to pick who the single dirtiest fighter is though...
Growing up I always heard that Fritzie Zivic was as dirty as they come. From lacing to thumbing to head butts, Zivic was the master. In more modern times, Eusebio Pedroza and Evander Holyfield were pretty bad.
After doing a quick search, looks like Mysterious Billy Smith (10 DQ losses), and Arnold Sheppard, who had 18 DQ losses, which I believe is a record, might be 1 & 2. Sheppard had a whopping 309 fights.
Not at the top but just how dirty Mustafa Hamsho was never seems to come up nowadays. He was one dirty mofo!!! For actual effect Luis Resto is worthy of mention, he indirectly cost a guy his life with his cheating. Someone that never gets talked about but had one subtle yet powerful pair of elbows was Michael Spinks. He had a few other tricks too.
Fritzie Zivic is generally recognised as the king of dirty fighting but opponents like Sugar Ray Robinson and Billy Conn said they learned more about boxing from fighting him than from anywhere else. And he ducked no-one. John Conteh knew were to place his head, so did Evander Holyfield and Mike Tyson took being a carnivore a bit far. Rocky Marciano always got upset when he was called a dirty fighter and denied doing it intentionally.
I've still got a boxing magazine covering that fight, it was ******* disgusting and whereas Zivic and Marciano's dirty but honest fighting could be witnessed and grudgingly admired, that was plain cheating. Collins could tell what had happened when he shook gloved hands with Resto at the end.
Bernard Hopkins he was worst because he does every foul to opponent & also then fakes injury to get time.
Resto, with the cushioning removed from his gloves, and the plaster of Paris on his hand wraps against Collins is the dirtiest single incident in my opinion. Resto's trainer Panama Lewis was corrupt beyond belief.