Slade Willson

Slade Willson AKA Deathstroke is a villain on Teen Titans/Titans and he's on Batman as a villain and he is Robin's AKA Richard Greyson's arch nemesis and once he even had hallucinations of him after his death. Once he also manipulated Terra to join him in battle against the Titans. (sorry about the image, it was the best picture i could get)