(All-Star Comics 005, 1941)
Mister X is another team comic overboss, like the Leader before him. Outwardly an unassuming little man, he has managed to gather a wide range of organized crime under his control while remaining completely anonymous, even to his own underlings. His only mistake (and the inciting event of the story) is being so threatened by the crimefighting activities of the Justice Society that he mobilizes his forces in an attempt to kill them even though they have no idea that he actually exists.
Even after they are variously attacked by gangsters, gamblers, car thieves, muscle men, criminal scientists, arsonists and magicians, the Justice Society doesn't actually end up catching Mister X. As seen above, he chooses to turn himself in rather than, say, relocating to South America or attempting to go into finance.
I quite like Mister X. It's hardly a novel idea for a meek little guy to be a secret criminal mastermind - like old ladies, guys like Mister X were accorded so little respect in the popular culture of the 40s that the idea of them being in some way formidable was a cliché long before this comic came to be. It's well executed here, with X being so unassuming that criminals and crimefighters alike are merely nonplussed when he shows up at the scene of crime after crime.
Absolutely the best thing about Mister X, though, is this bit about the moment of silence every time his name comes up around a bunch of crooks. They do it throughout the issue!
