(Detective Comics 041, 1940)
What makes them a super-villain? He's an espionage guy with an invisibility formula.
What is interesting about them? Invisible guys are often pretty dull comic book villains, but I will give the Invisible Man/ Dr Ellis this: his cover identity is as a scientist in the team that is trying to catch him, and he's evidently arrogant enough that he actually developed a formula for a gas that would render him visible again but assumed that investigator Cliff Crosby would not have the chemical knowhow to synthesize it. He was wrong!
