Effects of Obliteration

https://archiveofourown.org/works/755...

“I watched a documentary on the bombs dropped on Nagasaki and Hiroshima a while ago. In the blast radius, sometimes a… a person blocked the bleaching effect of the radiation. So the person was vaporized, but a shadow was left behind, on a bridge or a wall – their shape, their outline, when they were completely gone," Steve said. "It’s called a nuclear shadow.”

“If you’re implying the Soldier is like a nuclear shadow, then that is seriously fucking dark, man,” Sam said dryly.

OR

Before the fall of the Soviet Union, the Winter Soldier was sent to the American arm of Hydra - only there was a malfunction in the cryo-unit that meant it couldn't be opened, and it was left, powered but abandoned, in an underground base.

25 years later, the Avengers find it.