Created by Marv Wolfman and George Perez, Deathstroke originally appeared as an antagonist in “The New Teen Titans” #2 and first encountered Batman in the “City of Assassins” storyline of his solo series. A mercenary and assassin, the character has gone on to become a villain for multiple other characters, up to and including Green Arrow. In addition to “Arrow,” Deathstroke has appeared in “Lois & Clark,” “Smallville,” the animated “Teen Titans” television series, “Young Justice,” and “Beware the Batman.”
Affleck’s tease follows “Arrow” executive producer Marc Guggenheim’s comments about the character, who appeared as a primary antagonist in the first two seasons of the popular CW series. In February, Guggenheim told fans, “The character of Slade Wilson [Deathstroke] is currently tied up in another DC project.” From the looks of Affleck’s video, it appears that Deathstroke might just show up in “Justice League,” at least briefly.
Source : CBR