It would have had to be Monzon for me because I was a light heavy weight at that time. Roberto Duran is the man who is responsible for me becoming a fighter.Both men were very scary you really did not want to have any problems with either one of them. Great question.

As a lightweight it would be Duran, out side the ring in the street it would be Duran who was raised fighting for his life as a street person.

At middle weight it is Monzon, who was a much better middle weight than Duran.

Duran was scarier. He dominated lightweight in similar fashion that Monzon dominated middleweight, but then Duran went up a few divisions and whopped Leonard, only lost the rematch when he was out of shape, he was getting old but he could still compete, then he went up again and had a close loss to the middleweight the prime king Marvin Hagler, then when Leonard got the middleweight title he dodged Barcklay, Barcklay then kayod Hearns and guess who went after him? Duran! Duran whopped Barcklay, lost another to Leonard and kept fighting. He fought much younger Camacho and almost won while Camacho knocked Leonard out.

Look up the International Boxing Research Organization, their top 10 p4p of all time are all men who are born fighters. Duran was born a fighter, he began boxing in 1968 and retired in 2001

Roberto Duran is scarier if you DARE pick a fight with him both in and out of the ring. Carlos Monzon is scarier if you were either his wife or his children based on his history of domestic abuse with his family(particularly his ex-wives).

Duran

Duran was way more intimidating than Monzon. Duran was like a real life tazmanian devil when he was at LW.

you real? that like to ask who more scared Floyd or Foreman? hehehehe.