If someone were to ask me who I thought the most ruthless and murderous of all mob bosses was, my answer would most definitely be Nicodemo Scarfo, aka "Little Nicky" Scarfo of the Philadelphia crime family. He was Boss of the Philly Mob in the eighties, and was a far cry from the former long-time Boss in Philly, Angelo Bruno. Scarfo was well known for his hot temper and his quickness to resolve any problem with violence, including having his own men killed. His former crew members admitted that they all feared him because he was so unpredictable and violent. A well known case of Scarfo's extreme violent side was when he had Salvatore Testa, his right-hand man, murdered because he felt Testa was becoming too much of a star within the family, and he felt Testa would be a threat to his position.

I can't think of another Boss in Mob history where their crime family was so dysfunctional because the wiseguys in the family never knew which one of them the boss was going to order to have killed, no matter their position in the family. Scarfo was paranoid and would have a man killed for the slightest infraction.

Scarfo was eventually arrested, convicted, and sentenced to life in prison. He's still alive, in his 80's I believe. Albert Anastasia and Roy DeMeo may have been equally as murderous and cold-blooded, but Scarfo's reign as Boss nearly brought down his own family because of his extreme violence.