I made this way back when Overwatch was first announced, showing Angela's (Mercy) graduation day from med school, a little bit of my personal take on her ackground, would have had her lost her parents during the omnic wars and raised on an orphanage, there she would meet and become friends with another little girl, a bit younger than her. Her name was Zawadi, her parents had been killed while visiting the country on a business trip and she had been cut off from her country because of the war, ending up in the same orphanage as Angela, eventually becoming as close as sisters through her time there together.
Finally, Mercy got set up for adoption by a german couple, but both kids were attached to each other, that they both got adopted together.
They both lived happy with their adopting parents, all was well until Zawadi turned 8 years of age. She contracted batten disease, their parents did everything they could for her, but their efforts were in vain and she died shortly after, leaving a scarred Angela who would spend all her time tending to her sister, now gone.
This ignated a strong passion in Angela for ensuring none had to go through something like that ever again, she swore, if she could not stop people from dying... then she would bring them back.