Bruce
He never did get over her.
For all his PHD's, Bruce could never figure out the right formula for kicking Nat, err Romanoff, out of his mind. (Perhaps that was where he should have started, by calling her the latter.) Alcohol only blurred his memories and messed up his realities. (Plus, it made him think of the bar and when Steve told him to go for it-focus Banner.) Work helped, but stress brought dreams of her and that wouldn't do either. Hulking out didn't erase her either, seeing her only brought him back.
He couldn't put his finger on what it was about her that attracted him. She was beautiful, yes, but he'd met thousands of pretty women and this wasn't it. Romanoff had danger wrapped around her finger and love on her hip. An intoxicating reaction. Almost like a drug, except the drug did everything in its power to avoid you when you had it.
Perhaps it's a mark of his character that he couldn't get rid of her. Maybe it proves that he truly is an Avenger. What was it that Steve said?
They'd set up a memorial to her at Clint's farm. A piece of Pine wood, which Clint's family had carved into the Black Widow's sign. They'd lowered it into the hole and stood over it while Clint fumbled with a shovel. Fury muttered a few words about how much he admired her spirit. Pepper recounted her first encounter with Natasha, eyes red. Clint refused to speak, he was obviously too worked up to even try. It was the Captain who rose to the occasion.
"Nat was a true Avenger," He gripped Clint's shoulder and went on. "Some move on, but not us, that's what she said to me. We were her family."
Bruce clung to his words long after they'd filled it in with dirt. There was something beautiful in them. The idea of a group of people who physically incapable of ignoring evil comforted him. It immortalized them. Transformed them into heroes. People loved by Natasha Romanoff.
He liked the idea of her as a hero.