The Anti-Superman Gang was a criminal organization whose purpose was to learn about and defeat Superman.
The gang was lead by John Kiley, who used detectives to determine that Superman was likely Clark Kent. He was able to fool Kent into revealing his secret identity, under the pretense of being on his death bed. Subsequently, the gang lured him into a Kryptonite trap, which Supergirl and the Superman Emergency Squad helped him escape from. The gang was defeated and jailed by Superman. ("The War Between Supergirl and the Superman Emergency Squad!")