His face flickered as if she had struck him with the sword. It was the worst possible time for a conversation, the worst possible moment to tell her the truth. She was already in league with Morgause, she hated him and would hate him more. The castle was under siege, Arthur could have been hurt. But Merlin felt it in his heart. 03x02 Magic Reveal! The Tears of Uther Pendragon II

Natasha's been sent to collect or protect Bruce a little earlier than intended, whichever comes first. She's not surprised it's the latter. To evade capture, they go on the run with the US Military on their heels and the threat of the Hulk following like a shadow. All things considered, though, Natasha doesn't mind too much. The Doc's pleasant company - when he's around, that is.

Two years after the Snap, Bruce has been locked away in a lab of his own volition, hoping not to hurt anyone while trying to figure out what his problem is with the Hulk. But when he gets a call from Steve about Natasha, he knows it's time to stop running. It's time to go home. One-shot. Endgame compliant.

My response to an Endgame prompt by WeirdWarrior. Summary inside because SPOILERS!

Takes place during Endgame. A moment between Bruce and Natasha. The most important moment in the Universe.