Slade Wilson, better known as Deathstroke, is a supervillain from DC comics and one of the world's deadliest assassins, he is also known by the full title of Deathstroke the Terminator and was indeed originally named simply "Terminator" - though Deathstroke was added soon after. He was notable as the main antagonist of Judas Contract and Titans Hunt. Compared to the more powerful Trigon Slade isn't actually the Biggest and Baddest but he is the most recurring villain of the series and serves as the Titan's archenemy as well as Nightwing's.
His real name is Slade and it was this name that was used to base the main antagonist of the cartoon series Teen Titans (although as stated above despite sharing a common name they are different villains). His name in the comic books, Deathstroke was not accepted to be what he would be called in the animated 2003 television series, so he is only called Slade.