I don't own Young Justice! I mean, seriously, you would think people would know that by now.
The man walked casually down the street; well, as casually as you can look when you're searching for a child to perform a villainous experiment on.
He had several candidates, but none experienced the level of abuse that he needed to ensure that they would use their powers for evil. His toxin could not be wasted on any old orphan, especially if they had any kindness left in them. A child with the powers he was about to give them would be an immense threat if they used them for good, particularly if they were discovered by the Justice League.
The man turned right into a dark alley, scanning the road as he walked. There! A sleeping baby, lying alone in her carriage. He looked around quickly for the mother, and saw a wiry woman smoking a cigarette behind the corner of a shop. Yes, this baby would grow up mistreated, especially if the parents found out about her powers. As the woman turned away from the child, the man quickly took out the syringe, plunged it into the baby's arm, and was gone.
He was not there when the mother returned. He was not there when she screamed to see the baby emitting white tongues of lightning from every pore in her body. He was not there when the baby's parents argued long into the night about what to do with their little freak.
But he was there as the baby grew. He was there when the toddler, at age three, said happily, "Look Mommy! I'm fwying!" He was there when the child's bed was discovered soaked through with water, and the only explanation she offered was, "Pwetty clouds." And as the child grew, and as the man spied on her constantly, he discovered that no matter how much her parents fought, no matter how ignored she was, she found comfort within herself and pushed through. And as months became years, and a child became a teenager, the man could no longer be found near the house of the Jensens. He had given up. The girl was a failure, and he was wasting his time.
And so the world ignored the girl until, on the eve of her twelfth birthday, Rae summoned a storm.