A few past and present that come to mind are

Aaron Pryor
Jack Dempsey
Mike Tyson
Muhammad Ali- He had a hell of a mean streak
Vitaly Klitschko
Bernard Hopkins


Emmanual Augustas (Anyone remember what happened to courtney Burton for talking shit after winning their first fight)

Chavez
Floyd Mayweather


all dangerous men that when angered have the ability to control their anger with the exception of Tyson who would just wait for you in the parking lot after the fight