William Randolph Wintergreen grew up in Oxford, England. He worked with MI-5 and the British Army. When he was working in the British Army he met Slade Wilson. The two became close friends. When General Sampson sent Slade Wilson on a suicide mission, Wintergreen charged in to rescue Slade disobeying Sampson’s orders. Wintergreen was transferred closer to Slade after he met Adeline; Wintergreen later became the best man of Slade in his wedding. In revenge of what Wintergreen did years ago, General Sampson sent Wintergreen on a suicide mission. When Slade received word that Wintergreen was being a prisoner of war he went to Hanoi to rescue Wintergreen. Because of the rescue, Wintergreen felt he owed Slade his life
After the divorce between Slade and Adeline, Wintergreen became Slade’s right hand man, acting alternately as moral conscience, comrade in arms and nursemaid (Similar to the relationship between Alfred and Batman). Wintergreen helped Slade to fulfill a H.I.V.E contract to capture all members of the new teen titans, however Wintergreen felt that it was a wrong decision to take that contract and ally himself with Terra. When Slade started hunting in Africa, Wintergreen went with him and stayed at his side. After some time Slade returned to be a mercenary, only this time with a code of ethics. Wintergreen continued as the right hand of Slade.
When Rose's mother died, Slade fearing that he would not be a good father; left Rose in the care of Wintergreen. Wintergreen did a lot for Rose, even to the level of wanting to adopt her. When Deathstroke suffered a explosion that killed him (returned thanks to his immortality) he lost all memories and broke all relationships with Wintergreen.
When Deathstroke discovered that the spirit of his son Joseph (Jericho), was taking refuge inside his body he asked Wintergreen’s help to have an exorcise and get rid of the spirit. Jericho (in control of Deathstroke’s body) killed Wintergreen. Wintergreen’s dying words to Deathstroke were: "I suppose it was only a matter of time." He was then decapitated and mounted to the wall where Deathstroke had kept the heads of animals he killed as trophies.
In Teen Titans: Cold Case, Wintergreen's head is still mounted on the wall and Deathstroke talks to it.
A Resurrection of Sorts
Wintergreen is brought back to life as a Black Lantern and he and the rest of Deathstroke's dead immediate family attack Slade. Wintergreen says that he and Adeline aren't mad about Slade killing them, but Slade knows that they aren't the real Wintergreen and Adeline and continues to fight them. He is destroyed when Jericho takes control of his body and forces it to take the heart of Adeline Wilson, who is a Black Lantern. The two end up destroying each other when Jericho makes them try and take each other's hearts.
Wintergreen is an African American in the new 52. He was captured in Somalia and Slade rescued him as a rogue agent when the government denied his request to rescue Wintergreen officially. Wintergreen was Slade's only friend attending Slade's and Adeline's wedding. How he died is unknown and it is easy to surmise he had a close relationship with his son, who was at the Wilson's house when it was attacked. His son chose to stay and work with Slade when he became Deathstroke.
In Rebirth Deathstroke is led to Wintergreen, who had been held captive.
Wintergreen appeared in Teen Titans TV series, he was Slade's butler and a minor character. He first appears alongside Slade in "Divide and Conquer", where he served Slade tea as he watched Plasmus battle the Teen Titans. Sometime later, in "Homecoming Part II" Wintergreen was recruited into the Brotherhood of Evil. In "Calling All Titans" during the final battle between the combined forces of the Teen Titans and the Brotherhood of Evil, he was seen fighting alongside the H.I.V. E. Headmistress. He was premused defeated and flash-frozen along with most of the other villains in the Brotherhood.
Wintergreen also made a cameo appearance in "The Lost Episode", where he is seated beside the H.I.V.E. Headmistress in the audience.
Wintergreen appeared in his first live action portrayal in Arrow TV series, portrayed by Jeffrey Robinson. He appears as Slade Wilson's partner, and wears his same mask. He arrives on a deserted island in search of Yao Fei, but when he's captured, along with Wilson, by Edward Fyers, he betrays his partner and joins the mercenary. He tortures Oliver Queen on the island, and is ultimately killed by Slade in a sword fight.