Please Let Me Earn A Happy Ending
Instead of Pietro, Wanda dies in Sokovia. He stops in the middle of the battle for a moment, then continues to fight. Afterwards he keeps close to Vision and claims to have a headache.
He's taken to New York to be under supervision while the situation with Ultron is investigated. While there, he makes an apology video and posts it online where he explains his and his sister's role in the creation of Ultron, attack on Johannesburg, attack on Seoul and the battle and destruction of Sokovia, apologizes for his part in it all, including enabling Wanda, says that he accepts all responsibility and any punishment that will be deemed to be appropriate for what he did but that he wishes to also use the powers he has to help people and reveals that he had mostly gotten over his hatred for Tony when Wanda convinced him to volunteer for powers with her, but after that everything became kind of hazy and he "knew" that whatever Wanda said was right and he "woke up" at the moment of Wanda's death, which doesn't excuse his actions but could help understand the actions of other people she controlled.
Later Tony forgives him, and takes him under his wing, when Pietro refuses to follow Steve due to him attacking a teammate on the word of someone who had attacked them all before and is known to hate said teammate, and he is very happy with learning how to be a normal person alongside his new brother Vision. He also convinces Vision and FRIDAY to help him extract and fix JARVIS's code just in time for Tony's birthday.