Burt Kenyon a.k.a. the Hitman
A Vietnam veteran and skilled soldier, Burty Kenyon served alongside Frank Castle, while the two were in Vietnam. He even saved Frank’s life during a close encounter with enemy forces.. Kenyon told Castle that one day he would owe him a life.
Kenyon donned a costume while working a mercenary and hired killer in NYC. He’s gone after high-profile figures like Spider-man, but failed, after which the Punisher began tracking him down.
Ultimately the two faced off in a rooftop battle where the Punisher shoots Hitman. Kenyon was trying to kill J. Jonah Jameson but both Spider-man and the Punisher were able to stop him. Toward the end of the battle, Kenyon a.k.a. the Hitman is wounded and hanging off the edge of the building begging the Punisher to save his life.
Castle has to make a choice, he’s in the position to either save Kenyon or Spider-man & J. Jonah Jameson, the Punisher chooses the latter. He quips that he owed Kenyon a life and now he’s saved two, absolving him of a debt.
During the “Suicide Run” story line after the Punisher is presumed dead, Kenyon alternates his suit and begins his own career as a masked vigilante dressing in black with a skull mask, similar to the Punisher’s own design. Once Castle came back to NYC, Hitman ceased his vigilantism as well as wearing the similar suit. Probably for the best.