Slade

Slade Joseph Wilson (a.k.a. Deathstroke the Terminator)  or commonly just called "Slade", is the archenemy of the Teen Titans, as well as their greatest enemy. He is rumored to make an appearance in season 2 of Teen Titans Go!

Bio
Slade is the Teen Titan's greatest enemy, particularly Robin's, who will stop at nothing to destroy them. He is best known as the world's greatest mercenary. Slade has not yet made an appearance in Teen Titans Go!

In Terra-ized, Terra uses Beast Boy to steal information from the Titans for Slade. Though he is not seen or heard, Terra does call him in one point of the episode. Terra fails to bring the information to Slade when Raven banishes her to another dimension, which later reveals to be a trash hole in Be Mine.

Slade makes a brief appearance in the comic Silicon Valley Cyborg. When Robin asks Cyborg if he can be the VP of security, Cyborg tells him that he has already given the job to Slade. And with that, Slade sneaks up behind Robin and smacks him in the head.

Season 1

 * Terra-ized (Spoken to but not seen)

Comics

 * Party Party (cameo on cover)
 * Silicon Valley Cyborg (debut, cameo)

Trivia

 * At the TTG Comiccon panel 2013, TTG's creators stated that they wanted to use Slade and Blackfire for the series, but they were unsure if they would be able to. However, Blackfire has been confirmed to make a reappearance in season two, and Slade is rumored (yet still not confirmed).
 * The writers of the show have stated that they CAN use Slade, and they WANT to use Slade for the series, but are not sure HOW to use him (A dark, serious villain) in the show's silly format.
 * Ron Perlman reprised his role in the 2013 direct-to-video release Justice League: The Flashpoint Paradox.
 * He was one of the primary antagonists of the original series and was one of only two villains to appear in all five seasons (the other being Gizmo). Slade and Red X are the only villains to not be captured at the end of the series.
 * In the new series, The H.I.V.E. Five replaced Slade as the main antagonists.
 * He is also one of only two villains in the original show to switch sides (the other being Jinx). However, once his "revenge" was complete, he continued to be an enemy of the Teen Titans.
 * Slade's role in the first animated series is somewhat different from depictions in the comics, in the sense that he is a pure evil criminal mastermind, rather than a prominent mercenary who only leans evil and sometimes even fought for the Titans. However, he was willing to work for others if it benefitted him (as he did with Trigon, before the demon betrayed him).
 * The arrow in the Slade doll could be a reference to the CW's hit TV show ARROW, in which Slade is the main antagonist of Season 2.
 * In the original series he had Cinderblock, Plasmus and Overload as his minions, it is unknown if he still does like he has Terra as his apprentice.
 * He shares similarities with the marvel character, "Deadpool". In fact, Deadpool was created so much like Deathstroke, the creators decided to acknowledge that fact and made them him even more like Deathstroke.
 * He wasn't in the digital download of Silicon Valley Cyborg.