Ugh, I don't know what to do. This idea randomly came to me when listening to Whispers in the Dark by Skillet.
Marvel Fandom - Bucky Barnes based. OC has been an orphan all their life. They grew up fending for themselves. They enlisted into the Marines. Participated in the Afghan Wars. Has PTSD and became a Veteran. While Bucky is on the run between Captain America: Winter Soldier and Avengers: Civil War. The two randomly meet at a stowaway train, and they become friends. OC is the only "thread" to Bucky's humanity. If something happens to OC, Bucky will become the Winter Soldier and might not be himself anymore. [Not sure if OC should be a girl or a guy.]