Let’s talk about a Winteriron Leon AU, because I don’t remember reading anything like this? (If there is, pls I need the link).
Leon/Bucky is a hitman, lives alone in an old building, loves to nurse a plant (cacti, i love cacti) and is antisocial. He doesn’t remember anything of his previous life, he just knows what he needs to do, and that is boss name is Pierce. His last job is to watch the Stark, and report about them, and he do that. Watch and report.
Tony, is the only son of the Stark, Howard is the head of the biggest weapon factory in the world, but Tony hates with all his heart that work, and his family, but not his butler, he loves him with all his heart. One day when he is out, after a fight with his father, his family is killed, and Bucky witness everything, but he can’t do anything, that’s not his job.
Tony when he goes back home, find his family and Jarvis murdered, that’s when he decide to go to the “not so stranger” (he saw Bucky lurking around, and did some research he is a genius after all), so he goes to Bucky for help to take revenge on the people who killed Jarvis. Bucky tries to make him go away, but Tony just makes himself at home and doesn’t move from the house, and like that start their awkward house sharing, with Tony on a side that tries in all the way to convince Bucky to work for him (money at first because that’s the only way he knows thanks to his father, asking, begging because that’s the only option he has after everything), and Bucky on the other that on the first night tried to kill Tony, failing because he can’t kill a kid, he just can’t (maybe his memories are a mess, but he will never kill a kid) and after because Tony start to grow on him, he start to get attached, and his feeling start to change.
But one day, maybe after months? Tony just disappear, leaving behind a little note where he tell Bucky that he is going to revenge Jarvis alone, and kill Obi (the one that plotted to kill his parents).
Bucky after reading that little note, left behind with money and an extra note that tell him “to revenge his death,” just run to save Tony, and he actually succeed at that making the building explode with him inside and Tony safe outside passed out.
When Tony wake up in an hospital, find out what Bucky did, and is devastated, but he moves on taking back Stark Industries and changing everything.
Move forward to years later, where Bucky doesn’t remember anything again (Hydra took him back and deleted all the info about that mission), Tony found out and start HIS mission to take Bucky back with him and save him.