I didn't have to time to read everybody's answer on each page and everybody gave fantastic answers but did anybody mention Richard "ice man" Kuklinski? This son of a bitch was brutal but I heard that he exaggerated a little and took the credit for murders he didn't really commit. Also... Mad Sam destefano from Chicago was a absolute psychopath. Frankie Carbo from the lucchese's put in A lot of work during prohibition and in the murder inc era. And whitey bulger ...... He was a nut job !! No exaggeration there. He killed a lot of guys in the 70's and 80's alone. Gerry pappa that was in the Brooklyn faction of the genovese family was another nut with a gun!