Dr. Blitzmanns chemicals were supposed to have him grow in to a six feet athlete. Instead, due to Eve Blitzmanns mistake, he grew up at least a hundred feet.
He immeadiately begun to menace the world. Kidnapped Eve (who he was fond of), and trampled on. Wrecking buildings, killing people just for the sake of being a giant. Wanted to rule the world.
Defeated the attacking Phantaliens, saving Earth.
Then he headed for Europe. But that wouldn`t be seen until his second appearance. Which wasn`t printed.
Unlike the cover of his first appearance shows, he had no armour. Didn`t need one.