He leans towards the door, and the kid hesitates before reaching out to meet him. Tony's confused at first, before he feels wiry arms tighten around his back. Oh, hell, he thinks. He stiffens, unsure of how to react. "That's not a hug, kid; I'm just grabbing the door for you."
"Oh, oh, right," stutters the kid. He lets go as if burned, his eyes going wide.
Tony laughs it off with some sort of quip, but he's less focused on what's coming out of his mouth and more on Peter avoiding his gaze like it's the plague, face bright red.
Tony has never been one to get attached.
For years, there were women whose names he forgot, there were friends he pushed away. 'Isolation as a defense mechanism' is what the one therapist Pepper forced him to see called it.
Tony's lost enough. The security footage of his parents' death now seared into his memory certainly reinforced that fact.
And yet.
And yet, looking at Peter, eager and earnest, Tony can't help but feel a wave of protectiveness wash over him. The kid starts back to his apartment, shooting one final shy smile behind him, and Tony almost waves back.
Almost.
…
He's frozen as the Guardians crumble away, one by one. Fear has left him rooted to the spot, only able to watch the ash wheel into the wind.
He almost knows what's going to happen before it does. When the high, terrified voice reaches his ears, he meets it with a terror so strong it threatens to swallow him whole, and the soft, but persistent resignation that nothing he loves lasts.
"Mister Stark?" says the kid, his voice shaking. "I-I don't feel so good."
Tony wishes he were pinned to the ground with Thanos' sword again; it would hurt less than this does. His stomach drops somewhere around his shoes as the kid stumbles forward. Without thinking, Tony wraps his arms around him as tight as he possibly can, as if this will be his last chance, because he knows, knows that it is.
"I don't wanna go, I don't wanna go," Peter sobs, scrabbling for purchase around Tony's neck. His hands bury themselves in Tony's hair, trembling.
Tony lets him down, laying him into the dirt. Peter's dark eyes are glazed with panic; he's practically hyperventilating.
Tony never wanted kids.
Back when he was twelve years old and still 'Anthony, Howard Stark's son,' Tony made a decision. Even at that age, he knew children would not fit into his future, and that raising one would only be another responsibility weighing him down.
He could never be a good father. He wouldn't know what one looked like.
But somewhere in Peter Parker's absurdly trusting face, Tony found that he'd changed his mind.
That same face looks up at him now, ashen and seized by terror.
"I'm sorry," Peter manages to choke out.
There is a split second where Tony wonders if things would be different had he worked harder to keep Peter on Earth. They still would have failed; Thanos still would have snapped his fingers.
The only real difference is that the kid wouldn't have seen his death coming, would have gone out in a confused haze rather than this panicked shitstorm.
For that, Tony will never forgive himself.
In another universe, Thanos does not exist. In another universe, Tony goes to Peter's high school graduation; watches him walk across that stage and get his diploma with a smile so bright it lights up the room.
In another universe, Peter goes to MIT like Tony always hoped he would, and excels in his classes despite his extracurricular activities.
In another universe, Tony gets to watch the best kid he's ever known turn into the best man he's ever known.
In this universe, that kid dissolves into dust.
In this universe, Tony can only watch as the remains of what could have been are carried away by the wind.