I would certainly say Roberto Duran since he mauled one of the greatest fighters in the world. Jeff Fenech was a beast at cutting off the ring too. Even though he might be viewed as a cheater, Antonio Margarito was the ultimate pressure fighter and three more than most of the other guys. Between Margarito and Marciano, it was a toss-up. Ultimately I will go with Duran since he pressured elite fighters more often than anybody outside of Chavez. Marciano simply doesn't have the resume for me to consider him the most pressure fighter ever.

Mike Tyson & Mohammed Ali

Henry Armstrong.

rocky marciano , joe frazier

As much as I want to say Mike Tyson, I'd have to go with Roberto Duran. God knows how Leonard must've felt when 95% of the crowd cheered him on mixed with his natural born killer instincts.