Supreme has had a long, long career.
As an infant, the lad was adopted by the Crane family and named Ethan (it's entirely possible he was a stolen child and sold off to an orphanage. Same thing happened to Ric Flair) and was a fairly normal, if somewhat developmentally challenged, little boy.
At least until THAT day.
When Ethan was roughly four years old, he chased his beloved dog Radar into the nearby woods and found what appeared to be a meteor in a crater. Approaching the object Ethan began to feel sick and passed out, and may have died, if not for Radar dragging the child to safety.
When found by the Cranes both Ethan and Radar seemed to be near death, but slowly they regained their health. The most puzzling thing about this encounter was that the hair on both Ethan and Radar had turned a pale white. A local doctor whom the Cranes trusted later found the meteor and took it back to his lab to be hidden safely away for study and analysis. He believed the meteor to be a new element which he referred to as Supremium.
It would be noted that both Ethan and Radar both had some interesting changes in them physiology other than just their hair. Both seemed to gain enormous physical abilities, increased intelligence, and esoteric as it sounds....increased morality as time progressed. As he grew older Ethan would become known as Kid Supreme and save his home town of Liddlehaven and the world many times over.
And as he became a man he would be Supreme.
Using his vast intelligence and powers, Supreme would build his amazing Citadel Supreme somewhere over the Eastern Seaboard and in the 1940s and 50s do several amazing things, be it battling the evil Darius Dax, romancing Judy Jordan, or joining a team of heroes known as the Allies, which would occasionally team with the Justice Society and the Invaders (sometimes the three would be known as the 'All-Winners Squad' by the press). He however did not take part in World War II. Most metahumans did not, thanks in part to a mysterious being known as Parsifal, who had the power to remove the abilities of most metas with only certain individuals being immune to this ability (such as Captain America having no true powers, Namor being a natural Atlantean, or the Human Torch being an android). And there is absolutely no truth to the rumor that Supreme personally dropped Fatman and Little Boy on Japan.
By the 50s, Supreme and Radar would have a series of new adventures and allies such as when a mysterious encounter (and possible grandfather paradox) with the element Supremium endowed Ethan's new adopted sister Sally with powers similar to his. Sally would become known as Suprema and would follow in her brother's footsteps. Sadly Henry Moore, a reporter exposed to Supremium and took the name Wonder Man, would rather use his abilities to get laid. (It should be noted that it is believed that modern day crimefighter G-Girl may have gained her abilities from Supremium exposure as well).
By the 60s though, the times they were a changing.
That was when Gog came.
Gog attacked Astro City, a haven for metas, and decimated it. Many of the great heroes of the era came to do battle with Gog, Supreme among them. And many of the world's heroes died or were otherwise incapacitated (Wonder Man was one of the former, Mighty Man one of the latter). Even with the interference of a group of heroes from the future called the Justice League, who had pursued Gog from their time, it seemed Gog was unstoppable (By most accounts, history books show this as the first known appearance of Gog but as the insanely powerful being was traveling back through time, it was his last before being defeated).
Gog was only stopped when a trio of men who vaguely resembled the futuristic hero Superman appeared and soundly defeated him, promising to put him in a prison at the end of time with more of his kind.
Still the damage was done, and Supreme facing shell shock and depression decided to travel to the stars to find himself.
He stayed gone for nearly 50 years.
And like that, one day Supreme was back. Oddly enough one of the first modern metahumans he met was Superman, whom Supreme remembered from the 60s but whom from Superman's frame of reference had yet to meet Supreme. Supreme would oftentimes offer Superman advice, believing the younger hero would come to define this era just as he had his own.
Supreme would have several adventures such as saving Suprema and Radar from a sentient galaxy and battling the still living Darius Dax, who had taken to calling himself the Ultra-Humanite and after being altered by Supremium resembled a giant white ape, or manipulated into battling Thor due to Loki's mischief .
But all that came to end.
The Shi'ar came to earth one day, demanding Supreme surrender himself to their justice immediately. According to them Supreme had done battle with their champion Gladiator and interfered in the development and rule of several Shi'ar colonies. Supreme didn't dispute the fact, as something had happened to him while he was in space, something he could neither quite remember or explain, but that he intended to find out.
Surrendering peacefully and submitting to Shi'ar justice, Supreme was taken away.
What will become of him is unknown, but even in that final moment the greatest hero of the golden age reassured the world by looking back over his shoulder and winking.