One Panel #596: The Boomerang!

From Green Arrow: "The Boomerang" by George Papp, More Fun Comics #79 (May 1942)

I feel like Captain Boomerang stole this Golden Age Green Arrow villain his shot at returning (ha!), because the gimmick is pretty sound. He's the hitman you hire to get even with, and we do mean EVEN. Here the judge who condemned a criminal is killed in the same way and at the same time as the former. For detective heroes like GA and Batman, there's a lot of potential in the gimmick. Not only do you have to track down the dealer of poetic injustice, but you also need to arrest the person who hired him. Alas, this was his only appearance...