One is an alien scientist from the planet Aoron, the other a crime lord masquerading as the owner of Ace Movie Rental Agency. Each consumed with selfish ambitions intent on squashing any who stand in their way. Enter, the Green Lanterns!
First the scientist, who developed a star band providing him with immortality (at the cost of the rest of his race) and energy powers similar to Earth-One's Green Lantern, seeing the Guardians of the Universe as his rivals. Despite four confrontations with Hal Jordan with the powerful weapon and his invincible Starling minions, the man known as Evil Star never triumphed.
Next the crime lord Guy Pompton, who also assumed the alias of Evil Star manipulating matters with various stage gimmicks and his criminal gang to cover up aspects of a spilled script for a Stellar Studios movie that uncovered his criminal enterprises. Combatting various members of Earth-Two's Justice Society of America and leading each of them into defeat, it is ultimately the Green Lantern Alan Scott who himself overcomes Pompton, capturing the mastermind.