Who's This? The mastermind guy on page 1 of Who's Who vol. XIX.
How you could have heard of him: The Puzzler's real claim to fame, and perhaps that's why he got into Who's Who, was as a villain on the Batman 1966 TV show, a straight replacement for the Riddler when Frank Gorshin proved unavailable. He was played by Maurice Evans. Otherwise, you might have caught an appearance in 2010's Super-Friends #28, or might be more familiar with the new Puzzler, a woman called Valerie Van Haaften with a jigsaw-themed costume who premiered in 2002.
Example story: Action Comics #49 (1942) by Jerry Siegel and John Sikela
So the story begins with Superman saving a ping-pong champion from an explosive ball, and later from goons firing at a bullseye painted on the side of his car.
And what about the OTHER unethical character in the story? Clark "somehow" filed the story before she did. Nyah-ha. But what do you think? Should the Puzzler have had a longer and more illustrious career? Or is he the wrong kind of rogue for the Superman mythos?
Who else? After a lame, obscure Superman villain, how about a lane, obscure Batman villain?