In Superboy #67 (July 1958), a new Kryptonian makes his appearance in Smallville to taunt Superboy. Klax-ar claims it was he that destroyed Krypton with his “atron rays” for being exiled into space by a jury of scientists led by Jor-El. He agrees not to destroy Earth if Superboy willingly leaves Earth too. But Klax-ar just wants to steal Superboy’s super-strength, since he had lost his strength from over-exposure to atron rays. Turns out his Atron ray mine was a dud and never was responsible for Krypton’s explosion. While this isn’t quite the “Phantom Zone”, Klax-ar’s exile into space smacks very closely of it.
Known surviving Kryptonians: 1,000,006.