Warning: SPOILERS For Titans, Season 2, Episode 4, "Aqualad."
The latest episode of Titans confirmed the titular team's dark history with the assassin Deathstroke. While the show had previously hinted at Slade Wilson having a serious grudge against the team of young heroes, the details were largely kept a mystery until Titans season 2, episode 4, "Aqualad."
In the original Teen Titans comics, Deathstroke's grudge against the Titans was established in his first appearance in New Teen Titans #2. The action of the issue was largely devoted to an assassin called the Ravager attempting to complete a contract on the newly formed Teen Titans and Deathstroke's efforts to stop Ravager from overexerting himself. The end of the issue revealed that Ravager was Slade Wilson's estranged eldest son, Grant, and that he had undergone biological treatments that made him more powerful than Deathstroke but also tasked his body to breaking point. Blaming the heroes for pushing his son to the point of no return, Slade Wilson swore to fulfill his son's contract and take out the Teen Titans once and for all.
Titans establishes a similar backstory in the flashback episode "Aqualad." Set 5 years before Dick Grayson moved to San Francisco with Jason Todd, Rachel Roth and Gar Logan, the episode confirms that the first Robin once led a team made up of himself, Wonder Girl, Hawk, Dove and Aqualad out of the same tower base. It also shows Slade Wilson agreeing to take an assassination job in San Francisco, which is described by his associate Wintergreen as "an unusual one, but easy." While the exact details of the contract are not spelled out, it seems that Deathstroke was hired to kill the Titans. Near the end of the episode, Deathstroke kills Aqualad with a sniper rifle at a private airfield, which Aqualad had rushed to in order to stop Donna Troy from leaving Man's World forever.
Garth might be a target on his own, depending on his relationship to Aquaman and whether or not Arthur Curry is the king of Atlantis in Titans' reality. However, the fact that Deathstroke shot a second time at Donna Troy after bringing down Aqualad suggests that he was hired to take out all of the Titans and not just Garth.This would give the Titans ample reason to have a grudge against Deathstroke, but why would news of the Titans return drag Slade Wilson out of retirement?
The answer may lie in the final scene of "Aqualad," in which Dick Grayson is seen befriending a young mute man named Jericho, who Slade Wilson was seen watching from a distance earlier in the episode. Fans of the comics know that Jericho is Slade Wilson's youngest son and that he joined the Teen Titans as well, but it remains to be seen how Jericho's character will be developed on Titans and if Deathstroke's grudge against the team might tie into his fate.