Professor Aries, The Invisible Man

Golden Age Origin
Professor Aries was a criminal who figured out the secret of invisibility. He would put on a blue skin-tight outfit and dip himself in super...er...invisible ink. He eventually decided to quit using this secret for petty crime and to put it to work by raising an army of invisible mercenaries to take over the United States. His squadron of invisible planes bombed a US city, and his invisible mercenaries slaughtered quite a few US troops, before the Unknown Soldier managed to defeat the entire mercenary army by creating a tornado.

In addition to being invisible, Professor Aries appeared to be good with his fists, and usually carried a handgun.

Golden Age Appearances
Four Favorites #4