The intense backstory was probably Carol Marcus.
I would hardly call the reason behind her english accent to be an intense backstory.
Based on what Alice Eve mentioned about it, her characterization was written both as a generational conflict and a microcosm of the rift between Starfleet and Section Thirty One. Basically, Carol had a serious conflict with her father in a relationship that was otherwise very solid and uplifting until something happened that caused him to become all warped and evil. Her backstory would be as much about her disillusionment and lost of her father figure as the evolution of Alex's jingoistic fugue, and finally, Carol's ultimately futile quest to restore him to the man once was, "and should be again."
Too bad Khan crushed his head.