I was thinking on the story of Roy DeMeo and if there was in the other families a mobster that killed almost the same people Roy did.
So DeMeo for the Gambinos,Gregory Scarpa sr for the Colombos.
Another ideas? Also for the small families.

I'd say Tommy Pitera killed way more people than accounted for.

What about the Luccheses?

Georgie Zappola did a lot of work for the Luccheses.

And the Genoveses? Apart Vito Genovese,I dont remember wiseguys with a high murder rate in this family.

i bet people like Piddu Morello, Lucky Luciano or Joe Masseria killed many people before becoming bosses

Look up Carmelo Coppolino and Angelo Loele.

I've read somewhere that when Chin Gigante was running the family, he would give most of the murder contracts to the Jersey faction of the Genovese. I don't think there was any individual in particular who was doing the killings but overall, when Chin wanted someone to go, he woudl call the Jersey crew.