2. Damien Wayne
The son of Bruce Wayne and Talia al Ghul, Grandson of Ra's and the fifth Robin, Damien Wayne always comes up in every discussion about the Arkham Knights identity. Damien was born in an artificial womb after Talia - ahem - "procured" a sample of Bruce Wayne's... "DNA" and used it to create a genetically superior male heir for her father. After spending the first ten years of his life being trained by the League of Assassins, he arrived at Wayne Manor ready to aid his father in purging Gotham City of crime. Damien is more self-centered and ambitious than either Dick Greyson or Tim Drake and harbors a dark side that only his father Bruce can control. Though non comic book readers would be unfamiliar with the character, casual gamers may recognize him from Injustice: Gods Among Us, where he killed Dick Greyson and replaced him as Nightwing, serving under the evil Superman, who he considers more of a father than Bruce. In his personal epilogue, he defeats Superman, and joins the Sinestro Corps, due to his ability to inspire fear. Hey, he is the heir of the Demon after all. Though he could be too young to be the Knight, there have already been hints (okay, one hint) about his existence in the Arkhamverse. In Arkham City, Talia mentions sharing a night with Batman in Metropolis (which also confirms Metropolis exists in the Arkhamverse). Many believe this night could have led to Damien's conception (albeit more consensual than in the comics) and perhaps Ra's al Ghul has been training his grandson in secret. Now with Protocol 10 failed, Ra's may have one last surprise in store for Batman: pitting his own son against him under the guise of the Arkham Knight.