A/N: Characters and situations belong to Marvel Studios. This is darker than many of my stories.
He Who Fights Monsters
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you.
At first, Clint didn't have a plan. Like so many others following the Snap, he searched for his family, for his friends, for news. The former was impossible, but even the latter was difficult. Rumors abounded: nuclear radiation, the rapture. Clint, however, had resources others did not. After shedding the anklet (he'd only ever worn it as a concession to keep him near his family), he made a video call to Natasha. The relief on her face at seeing him lasted only briefly before being replaced by an anguish that mirrored his own.
She knew without him having to say the words. That was Natasha.
He choked out, "Sitrep."
Thanos. Mad Titan. The one who'd sent Loki and the Chitauri. Some kind of megalomaniacal scheme for population control. They had tried to stop it, but it was too late. The team (what was left of it) was returning to the Avengers headquarters to try to rebuild. The idea of building anything was laughable to Clint (Laura rolling her eyes at his latest remodeling project) or would have been if he could summon a laugh. He strapped on the weapons he was supposed to have surrendered after Berlin and set out to meet them anyway. He had nowhere else to go.
The trip was slow going. Three and a half billion people had turned to dust and vanished. Some had been driving; some had been flying. There were trains derailed, downed planes, and crumpled cars on the highway. Clint hiked through a wasteland into town. It was quieter than he remembered. Fewer birds chirped. He stopped in at a convenience store for a cold bottle of water. There was no clerk, but he left two and a half dollars on the counter anyway before continuing on.
SHIELD agents trained on how to function on minimal sleep during a mission, and Clint was no exception. When required, he had been known to stretch the limits of what was advisable. Eventually, however, he had to close his eyes. That was when the nightmares came - of reaching for Laura's hand to have it dissolve between his fingers. Of ruffling Nate's hair only for his hand to pass through empty space. Of patting Lila's shoulder as she disintegrated. Of pitching a baseball to Cooper and watching it sail through dust.
The first approaching footfall awakened him. That was something else SHIELD agents trained in, and it was a relief. He was crouched to respond even before he saw the guns. The hands that held them were steady, and the faces above them were covered. One week into the apocalypse, and the vultures were already flocking.
"We'll just take what you've got in that pack," said the first man from behind his mask. "Then you can go on your way. We won't hurt you if you cooperate." There were dark stains on his clothes. How many times had he said that? To how many people? How many times had he lied?
What had Natasha said about Thanos's plan? To revitalize the universe by culling the excess population. Apparently, he'd missed some.
It turned out Clint could laugh after all.
It was five years before he made it to headquarters.