scarfo sr. has that notion as one of the worst bosses ever because he literally killed his own family, same as casso/amuso.
From the sheer killings pov i would guess that the oldschool bosses were much more blood thirsty, esp in the 30s/40s... but they didn't bring down a whole family, like the ones mentioned first.

also, tony soprano was a horrible boss - at the end his family is more or less rubbed out.