Perhaps the most persistent pest to the family El of Krypton-One was the second cousin, once removed, of Kal-El/Superman known as Kru-El. Seeking to develop a stockpile of banned weaponry for his own sinister purposes, this black sheep of the El's was captured and incarcerated by Kal's father Jor-El. Banished to the Phantom Zone, Kru-El would routinely throughout the years work alongside fellow prisoners of the Zone such as General Zod and Jax-Ur to attempt to exact revenged against the son of their jailer. On one occasion, Kru-El was instrumental in designing creatures known as Anachronids who disrupted space time continuum, which directly involved his cousin and fellow Justice Leaguer the Flash. This parallels what occurred with his cosmic twin as to bending history to his will.
The several encounters between Man of Steel and Man of Malice on Earth-One were mirrored on Earth-Two by Kru-El's counterpart Vandal Savage... and another metallic man alongside Kal-L! We now consider the long running enmity between Vandal Savage as Genghis Khan vs the Shining Knight, Sir Justin!
As Superman, he would later redeem himself somewhat by leading a crushing defeat against Earth-Two's adult Genghis during an adventure with his fellow Justice League members, as well as that world's Justice Society and Law's Legionnaires. More on that later.
Several centuries prior to his appearance as Khan, as Vandal Savage this immortal was a feudal lord in England during the age of Camelot when he first encountered one of his most enduring adversaries, the Shining Knight. The Knight and his flying steed Winged Victory were investigating a massive dimensional tuning fork installed in the countryside next to Savage's castle by the ageless Monitor, placed there as well as four other key points in history on two earths to prevent them from being destroyed during the Crisis on Infinite Earths. While the Knight along with Earth-One's Firestorm and Ice Maiden defended this fork from threats originating in the Anti-Matter Universe, it was the marvelously metallic armored Knight who aroused Vandal's interest that would develop over the years.
As Khan, Savage was plucked from the thirteen century do the twentieth century by the renegade scientist known as Doctor Doome. The Doctor had developed the means to traverse time, and employed various notorious conquerors from history including Attila the Hung, Alexander the Great and Napoleon Bonaparte as well as Khan to lead Doome's minions in modern conquest. The members of Law's Legionnaires (or Seven Soldiers of Victory) were dispatched to deal with these individual threats, with Knight choosing Khan. No doubt, this battle helped Genghis to recall when as Savage he had first encountered the Knight. Once defeated, Khan returned to his native time. Perhaps during his foray into the future, Savage recalled his earlier meeting with another Legionnaire, Vigilante, when that hero was sent to Ancient Rome when Vandal was Julius Caesar.
Years later, the Legionnaires were thrust into the time stream after a battle with the Nebula Man, with each member arriving in a different historical era. Tied through the chronal device given to him by Doome, Khan was able to extract Shining Knight and bring him to the thirteen century in order to aid him in his conquest of China. It was during this occasion that the entity known as the Oracle dispatched teams of three heroes each to various eras in order to extract the Legionnaires and bring them back to their native era. Thus, it was Earth-Two's Sandman and Earth-One's Metamorpho and Superman who did this, with Superman's aforementioned victory versus Khan.
But this was not the end of Khan, as he would be pulled forward in time on one more occasion as a temporal phantom alongside other historical villains in order to battle the Patrol consisting of Fred, Pedro and Slim. Once returned to his earlier time period following defeat, Savage forsook being a direct ruler and instead assist others behind the scenes. As such, his first modern day appearance as Vandal Savage was versus first Green Lantern and then as a member of the Injustice Society versus the Lantern's Justice Society. He would return over the decades to battle the Society three more as well as the Flash of both earths. Eventually, Savage met his own world's Superman in ancient Camelot which he returned to in order to lead the Society into a trap and draw them to a planet of his own design in order to siphon the Man of Steel's power into himself. And the person who led Superman and the Society to Camelot to pursue Vandal? The Shining Knight who had a link to the villain throughout the centuries. Eventually, Savage moved to Earth-One for a few months, first attempting to change that world's history to make him a conqueror and later an insidious business man. After decisive defeats versus the Man of Steel and his old foe Immortal Man with the Forgotten Heroes assisting them, Vandal Savage disappeared from Earth-One.