Dark One
Everybody has a dark side buried within them. Most of us fight it; Khan embraced it.
He already had power, being one of the world's first genetically modified super soldier. Unlike the rest of the test subjects, his brain and body accepted the DNA rewriting, making him so powerful it would blow your mind.
But he was like a dog who'd gotten his first taste of blood--he wanted more. The power he had wasn't enough.
He endangered the freedom, and the lives, of the other young men and women who had participated in the same test. He didn't care. Didn't care whether they lived or died, didn't care how many he hurt in the process...
Obviously, Khan couldn't be allowed to run around. So, like the other test subjects, he was taken to a bunker way below the surface, locked into a cell that could withstand a nuclear blast, with another wall outside of that one, and one outside of that. There was a 24 hour guard, and they had the best tech available.
But one night, everything changed.
Khan escaped his cell. The facts aren't clear, but we are lead to believe that he killed several guards. The commander of the facility ordered the backup security system be put in motion--the facility was going to be imploded.
This was a hard choice for him to make, as his own father--the man who had rewritten Khan's DNA--was in there. But safety came before his own emotions, so the building was imploded.
Khan caused the death of the man who had cared for him since a child. And he didn't care.
Everyone thought Khan had died in the blast. Even the inner walls of his cell had collapsed. Only a huge, smoking crater remained.
And Khan.