Disclaimer: If I owned Harry Potter, I'd be a bit busy with my freakin' amusement park to publish stories on Fanfiction.
The moment Snape laid eyes on the child, he hated him.
The potions master watched with silent fury as Harry Potter, the Boy Who Lived, the Vanquisher of You-Know-Who, and the Son of a Bastard entered the Great Hall among a sea of baffled first years.
He was an exact replica of his father, right down to the last disheveled black hair. James Potter, the prat of all prats, had been Snape's main source of torture back in their school days, and he was certain that the boy would follow in his footsteps.
Even after he was sorted into Gryffindor ("Of course," Snape had muttered darkly) and joined the table farthest to the right, the professor continued to scrutinize him closely, finding fault with everything he did. If he took a pumpkin pastry, he was a pig. If he refused the pudding, he was ungrateful. If he was engaged in a discussion, he was intrusive. If he remained silent, he was haughty.
Snape preoccupied himself by conversing with the new Defense Against the Dark Arts teacher, Professor Quirrell, but he only half-listened to the turban-clad man's remarks as he periodically glanced at the young boy from time to time.
He thought he had been rid of Potter when the Dark Lord paid him a visit at Godric's Hollow. But now his successor was here to point out all the areas he failed in as James succeeded: Quidditch, popularity, the ability to decipher between good and evil, all the things that had been constantly thrown in his face during his years at Hogwarts.
He sneaked another glimpse at the object of his contempt, only to find the boy staring straight back at him. Their gazes met, and Snape got a first sighting of his piercing green eyes.
Her eyes.
Everything else surrounding them melted away, and before he knew it Snape was looking right in the face of Lily Evans. She was exactly as he remembered her, with her silky red hair, warm and inviting smile, eyes sparkling the way they always did when she was about to laugh...
The image shattered as soon as the boy broke the stare and returned to his meal, oddly rubbing the spot on his forehead where his lightning bolt scar resided. In an instant, he became James again.
And Snape resolved that was how he was going to stay. Seeing that one attribute of Lily's right in the center of all of James' would only make him recall of yet another thing, the worst one of all, in which Potter had gotten the better of him. He had stolen the woman he loved and always would love, and admitting that the two had both taken part in creating this child would simply mock him. It would serve as a painful reminder that had he not ruined his chance, James Potter's son might have been his.
Snape spent the following years avoiding looking at the child's eyes if he could help it. But the rare times when he couldn't escape those green eyes were moments of pure agony. He would see Lily's eyes full of anger directed at him, just as they had during the row that tore their friendship to pieces.
As time passed he watched that anger turn to resentment, growing deeper and deeper until it finally burst. The night Snape had murdered Dumbledore, unbeknown to anyone else that it had been done on the victim's orders himself, Potter had attacked him in a fit of rage, his mother's eyes gleaming in a vicious way that they never had before.
It was no longer anger, nor was it resentment. It was hatred.
And as Snape lay dying on the floor of the Shrieking Shack, he realized that he would never get the chance to amend that.
It was rather ironic that his past mistakes were becoming apparent to him when it was too late for them to be repaired. For Lily's sake he had done the bare minimum to ensure her son's safety, but on account of James he had done nothing more. In fact, he had made the boy as miserable as was in his power, all because of a former rivalry with his father. Was his hatred of James stronger than his love for Lily?
What's more, he'll never be able to complete the task Dumbledore had entrusted to him: to pass on the information to the boy that he must die, that the rest of the Wizarding World may live.
For reasons that had long escaped him, Snape had been truly disturbed by this. He told himself that it was only because he felt all his efforts to keep him alive had been rendered useless, that Lily had died for nothing. But it was when Dumbledore had lightly teased him, saying that he had finally begun to care about the child, that the full truth became clear.
Snape obviously denied the old wizard's suspicions, claiming he did it all for his mother, which in a sense was still true. He had at last allowed himself to see the Lily inside of her son, and he once again let her slip through his fingers, this time for good.
But speak of the devil, Harry Potter suddenly appeared before his very eyes.
Snape was surprised to see there was no emotion whatsoever in those green eyes- not hatred, not concern, not even pity. They were absolutely blank, a clean slate if you will. His opportunity to make up for everything had arrived.
He could feel the snake venom coursing through his veins as it rapidly spread throughout his body, but he managed to grab the boy's- no, it's about time he began to use his proper name- Harry's shirt and pulled him close.
It wasn't very difficult to choose the memories he wished Harry to see, for they had been endlessly playing over and over again in his mind. Taking nearly all that remained of his dwindling strength, he used his wand to extract them from his mind and offered them to Harry.
But there was one last thing that needed to be done.
"Look... at... me," he rasped weakly.
When those green eyes bore into him for the last time, he saw Lily. When he added the black hair and glasses to the picture, he saw James. But when he took in the person as a whole, for the first time since they met he saw neither. There was only Harry.
And as he felt the life seep out of his body, his final thought was one of regret that he was never able to move past the history with his parents to know him for who he truly was.