The Crime Czar
A highly secretive mob king. To bring him to justice, Superman makes a robot named Krag that appears to come from Mercury and has the robot challenge and defeat him to prove that he is good enough to meet with the Crime Czar.
Taken to the Czar's secret hideout blindfolded, Superman, disguised as Krag, finally unmasks him and takes him to the police. The Crime Czar is recognized as "Fleming... the Mayor's assistant" (Act No. 165, Feb 1952: "The Man Who Conquered Superman!").