Bobby Baccalieri Sr. is referred to in the series as "The Terminator" and is referenced as someone who's done many hits although I don't believe the exact number was ever said.

Chris racks up more than a few over the years too, from Emil in season 1, right when we meet him and later in the season Mikey Palmice (along with Paulie), to the cop that killed his father and even his AA cohort and business partner JT Dolan - he also orders a few including the guy in Boston who he sends Gene Pontecorvo to go hit. Whether or not he killed the Russian in Pine Barrens or one of the bikers after him and Tony rob them for the wine bottles together is left somewhat open, but certainly Chris was a stone cold killer.

As for Johnny Sack making his bones - I'm going to say yes. You don't rise up to that position without earning a ruthless reputation and several times in the show we saw his violent mean streak and the explosive temper that went with it. He would have been inducted probably in the early '80s or so and that being the case, I would have expected him to have made his bones for sure. He was respected by cold old school guys like Phil (until the wedding) who I don't think would have respected him without is having the reputation of a killer.

Carmine Jr.? I'm going to say most likely he did not. Thomas Gambino situation.

Tony B is also a great pick.

Overall it's probably somewhat unrealistic how many killings Tony, Chris, Silvio and Paulie in particular are credited with. But if I go back and re-read that Anthony Casso biography maybe I wouldn't be so sure!