4. Amadeus Arkham
Who better to take on the persona of the Arkham Knight than a member of the Arkham family? Amadeus Arkham is the founder of Arkham Asylum and he has a very dark and disturbing backstory (but then, who the hell doesn't in these Batman comics?). He euthanized his mentally ill mother, and after setting up the Asylum he discovered his wife and daughter raped and murdered by one of his first patients Martin "Mad Dog" Hawkins. Personally taking over the Mad Dog's treatment, Arkham murdered him with electroshock therapy, beginning his descent into madness. Ironically Arkham died as an inmate in his own Asylum. Though he has been dead for decades, we do discover that his grave has been dug up in the first game. Since Arkham already inspired Quincy Sharp to kill in his honor, it's easy to believe the Arkham Knight (the clue's in the name) could be a loyal admirer, or even descendant of Amadeus Arkham, if not Amadeus himself. It might seem ridiculous, but to date in these games we have seen a man with green scales convinced he's a crocodile, a woman who is more plant than person, a man kept alive by a robotic suit at subzero temperatures, a 600 year old man who continues to evade death, and an actual freaking zombie. Therefore, unlikely though it may be, we are prepared to let this game convince us that whoever is under that mask, doesn't necessarily have to be someone among the living.