William Wintergreen (Arrowverse)

William Wintergreen, also known as Deathstroke, is a major antagonist in Season 1 and a minor antagonist in Season 8 of Arrow. He was the former best friend and partner of Slade Wilson before he turned on him and joined Eddie Fyers' cause. 
== History==
In season 1, Wintergreen tortured a young Oliver Queen when he was stranded on Lian Yu to get information on Yao Fei. However, Oliver was rescued and made his escape. 
Billy Wintergreen later helped in capturing Yao Fei Gulong when he easily caught Fyers. However, Oliver was told to flee. As he looked behind him Wintergreen couldn't find Oliver and went back to Fyers ' camp. 
Later, when Oliver was nearly killed by Wintergreen, Slade came to rescue him by causing an explosion and engaging his former friend in combat. He killed his former friend and later escaped, with Oliver