'Killer' Maroni was a mobster who sent his henchman, Mike, to murder an important witness against him. The witness had already been seriously injured by a previous assassination attempt and was about to be operated on by Doctor Charles McNider when Mike threw a grenade into the room, killing him and blinding McNider. Maroni continued with his illegal operations but McNider, in the meantime, discovered that he could still see in the dark and became the costumed mystery man Dr Mid-Nite. Having saved another witness from Mike's inept attempts to kill him, Mid-Nite tracked 'Killer' and Mike down and turned them over to the police, along with evidence of their crimes. Maroni has not been seen since.

  • 'Killer' Maroni should not be confused with the mobster Sal Maroni, who operated in Gotham City several decades later.
  • This version of Killer Maroni (Earth-Two), including all history and corresponding appearances, was erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. Even though versions of the character may have since appeared, this information does not apply to those versions.