After the 80s has become more difficult to kill someone both because of the DNA, both of the different surveillance systems and the Mafia no longer leaves the corpses on the street preferring to make them disappear.

So first the 80s:

Murder Inc.
Forty-Two Gangs (Chicago)
East Harlem Purple Gang
DeMeo Crew

To 80s to now

Scarpa Crew
Tommy Karate Gang
The Ozone Park Boys