Shado

Shado was the companion of Oliver Queen and Slade Wilson during their time on Lian Yu and the daughter of Yao Fei Gulong and the identical twin sister of Mei. Unfortunately, she was killed by Anthony Ivo when he gave Oliver the sadistic choice of saving either her or Sara Lance
Shado's death would continue to haunt both Oliver and Slade, even years after the incident, and both. While Oliver remembered the light aspects of her, including her beauty and kindness, Slade often saw her as a dark and tragic figure, urging him to avenge her death by killing Sara and Oliver, making this one of the main reasons for Slade's vendetta against Oliver Queen and Team Arrow in present day until the Mirakuru was drained out of his system.
She was Oliver's lover and third mentor, after Yao Fei and Slade. Oliver would use her philosophical proton training when Roy Harper first became his protege.