Probably These guys....
Gerald McClellan
Julian Jackson
Sonny Liston
George Foreman
Mike Tyson
Jamie Clegg
Not necessarily in that order.
Fact is even a shitty boxer, who trains and fights regularly, would fuck up your average tough-bro.
But these 6 guys listed above, they'd definitely knock you the fuck out. Liston, Foreman and Tyson would probably cripple you.