Wikipedia
Deathstroke (Slade Joseph Wilson) is a fictional character who appears in comic books published by DC Comics. The character was created by Marv Wolfman and George Perez. He is a mercenary and assassin who first appeared in The New Teen Titans (vol. 1) #2 ( 1980). Wizard magazine rated him the 24th greatest villain of all time. Also, in 2009, Deathstroke was ranked as IGN's 32nd greatest comic book villain of all time.
Originally the archenemy of the Teen Titans, writers have developed him over the years as an adversary of other heroes in the DC Universe. Parallels have been established between him and Batman, and he has a deep-seated grudge against Green Arrow. The character has been substantially adapted from the comics into multiple forms of media, including several Batman related projects and the Teen Titans animated series. Slade Wilson/Deathstroke later appeared on The CW's live action TV series Arrow, where he is portrayed by Manu Bennett.