Surely the answer to this is vitali klitschko, how many fights has he won before even getting in the ring because the opponent was intimidated by how good he was.
Prime Tyson was terrifying. He wasnt going out to win a boxing match, he was going out to brutally hurt the other opponent
In Boxing you can not really have "A Most" "or Best This or That" Just a "Premier League of " so to speak, Many an intimidatating fighter has been mentioned, The middleweight division alone could boast a horde of them Carter, Briscoe, Barkley McClellan etc. but its interesting to note that it is usually a Cool Headed operator who uses basic fundermentals to slay these dragons, We the public may be easier to intimidate than a confidant in his skills Having said that...People like Liston did have ..er..Associates who may of lent an element of ..Concern to opponents lest they ruin some well laid plans
Liston, Foreman, Tyson, Duran and as somebody else mentioned Edwin Valero, he had a psychotic serial killer look in his eyes