If you have the Sword of Lightning, Sword of Cold or Sword of Fire (for characters who use bladed weapons) OR the Mini Gun, Panzer Faust 3, RPG, Stinger or Dragon (for characters who use guns), beating the Vaporizer should be a sinch.
ALSO: If you aren't being character-specific, using Dark Ages Spawn or The Admonisher will get through most heavy bosses like Cy-Gor, Overt-Kill, the Vaporizer, etc.
As long as you use those items and DON'T get caught in his noxious gas blast or his claw combo, you'll beat him in no time.