|“||Slade! Come back to die?||„|
|~ Wintergreen to his ex-partner, Slade|
Billy, as he was nicknamed by his friend and partner Slade Wilson, was once an agent of the Australian Secret Intelligence Service (A.S.I.S.) unit's Team 7, where he served under the codename Bishop. But when he and Slade arrived on the island of Lian Yu to rescue Yao Fei, Wintergreen betrayed his friend and defected to Edward Fyers' mercenary unit, where he adopted the identity of Deathstroke.
He is portrayed by stuntman Jeffrey C. Robinson.
Bill Wintergreen was originally a member of Team 7, an elite division in the Australian Secret Intelligence Service, where he was partnered with his best friend, Slade Wilson. The two men were sent to the island of Lian Yu to rescue exiled Chinese general Yao Fei from a group of mercenaries, who aimed to cripple China's economy. Upon arriving on the island, their plane was shot down and they were captured by Edward Fyers, the mercenaries' leader. Recognising their talents and abilities, Fyers offered the two men a chance to join him in exchange for survival. While Billy gladly accepted the offer, Slade declined, and was tortured by Fyers along with Yao Fei. Slade and Yao Fei eventually escaped, and Billy was tasked with recapturing them.
When Fyers captures shipwrecked playboy Oliver Queen, he tells Wintergreen to torture him for the location of Yao Fei. As Wintergreen tortured Oliver, Yao Fei arrived to rescue him, subduing Wintergreen and escaping into the forest. Wintergreen and the mercenaries then tracked down and ambushed them, with Yao telling Oliver to run while he holds them off. Wintergreen then duelled with Yao Fei once more, and the fight ended when Wintergreen overpowered his nemesis. Wintergreen then brought Yao Fei back to their camp, where Fyers blackmailed Fei into joining them.
During the night, Wintergreen would serve as entertainment for Fyers and the other mercenaries in an organised fighting circle, where he would duel captured prisoners while Fyers watched. After brutally defeating the prisoners, Fyers would allow Billy to kill them for amusement.
When Oliver returned to the camp to rescue Yao, he was knocked out and captured by the mercenaries. After speaking to Queen, Fyers allowed Wintergreen to beat and execute him. However, Slade caused an explosion to distract mercenaries. And as Oliver ran to safety, Slade engaged Billy in single combat. Despite Billy initially gaining the upper hand against his ex-partner, Slade eventually managed to defeat Wintergreen, and seemingly killed him by stabbing his right eye.
Despite being a man who once served his country, Billy revealed his true, treacherous and self-centred nature when he betrayed his best friend and partner, Slade, by joining Edward Fyers' mercenary unit. Billy also had a bad temper, as when Oliver called him by his name and criticized him for what he had become, Billy brutally attacked him.
Billy was a tall man of somewhat muscular build, standing higher than everyone he encountered, including Oliver Queen, Slade Wilson, Edward Fyers and Yao Fei. His outfit comprised of a slick black tactical suit complete with chest armor, shoulder pads, gauntlets, shin guards and multiple pouches. He also wore black kneepads and an elbow pad on his left arm. A belt was strapped to his left shoulder, which held three black and orange smoke canisters, and the sheath for his sword was attached to the back of this belt. His right leg sported a holster for his Desert Eagle pistol. However, the most distinguishable feature of Billy's outfit was his black and orange bicolored fabric balaclava mask, which only showed his eyes underneath, giving him an intimidating appearance.
- Military training: Being a man who spent years of his life serving in the military, Billy was a trained strategist and tactician when it came to planning military operations.
- Peak of human physical condition: Billy was a man in his physical prime who demonstrated feats of exceptional strength, shown when he snapped one of Yao Fei's arrows in half with one hand. He also demonstrated incredible reflexes for a man of his height and build. In fact, judging by his battles with Yao Fei and Slade, Billy's reflexes appeared to border on superhuman.
- Master hand-to-hand combatant and martial artist: Billy was a master in close-ranged hand-to-hand combat. He was also an exceptional martial artist, managing to defeat Yao Fei (who was already an extremely skilled fighter) in battle. According to Slade, Billy had especially effective kicks, which was proven when Billy used an array of kicks to pin Slade down during their fight.
- Master swordsman: Billy used a curved grey sword as his primary weapon, and wielded it with devastating proficiency. During his fight with Slade, Billy also used his tactical knife as his secondary weapon.
- Mastery of various weapons: As a former A.S.I.S. operative, Billy was an expert regarding various firearms and explosives, and was extremely skilled in using them during combat.
- On the show, Billy adopts the supervillain identity of "Deathstroke" before Slade does.
- Despite never being called "Deathstroke" in the TV series, Billy's season 1 concept art and his DC Collectibles action figure refer to him as such.
- Billy's being stabbed in the right eye by Slade is a reference to the Deathstroke character in the comic books, where he is distinguished for losing his right eye.
- Billy gives Oliver multiple scars on his upper body.