[sandycove]

Maybe a bit off the mark, but my view is that the gold standard in "bad guy" crime fiction is the Parker series by mystery grandmaster Donald Westlake, writing under the pseudonym Richard Stark. Most are now back in print.

Another great "bad guy" is Andrew Vachss' Burke. But he's an amoral independent on a moral crusade.

For shooting people, Stephen Hunter's sniper Bob Lee Swagger is without peer. He is not, in fairness, a classical hitman.