To date, we know that at least three characters are set to appear in the upcoming prequel, Arkham Origins: Black Mask, Deathstroke, and obviously, the Caped Crusader himself, and from what little we know about the plot, plenty more of his rogues gallery are set to appear as well.
The current defacto Gotham crime lord is Black Mask, who is bankrolling a number of assassins, as well as a few of Gotham's boys in blue to take down the up and coming Batman. Over the last 70 years, the vigilante's list of enemies has grown extensively, giving Warner Bros. Montreal an extensive list of characters to choose from. With two Arkham games already featuring some of his more well known villains, their options have been reduced a bit. They'll want to go with villains that have some bit of familiarity and recognition, but who haven't been seen in gaming yet.
The following are some of the better options:
Lady Shiva - Women haven't had the largest role in the Arkham games, featuring only Poison Ivy and Catwoman to date.
The character has a tendency of imitating noises in his surrounding area, hence the name. The habit comes across well on paper, and could make for an equally unique experience in a video game. Imagine tracking the villain, turning on a faucet, or knocking on a wall, just to get a sense of where he may be hiding.
KGBeast - If we're going back in time, might as well harken back to Soviet stereotypes of the Cold War era. Soda Popinski has nothing on Anatoli Knyazev, a well trained sociopath with a higher kill count under his hammer and sickle than Andrei Chikatilo.
He's a mediocre villain at best, but was truly dedicated to his craft, going so far as to cut off his own hand to avoid capture, armed to the teeth with the best hardware the evil empire had to offer. In the comics, he was little more than a tool of the Kremlin, but if Warner Bros. Montreal keeps the game in modern times, with the Soviet collapse, he could easily be motivated by a large sum of cash.
Prometheus - Everyone knows the origin of Bruce Wayne at this point, watching his upstanding, pillar of the community parents be gunned down at the hands of a lowly thug. Prometheus story is the exact opposite. His parents were Bonnie and Clyde-esque drifters, moseying from place to place, committing crimes, until they were shot and killed by police in front of their only son. While Bruce swore to take vengeance on criminals, Prometheus swore a similar oath against those who upheld the law. Taking his parents wealth, he too traveled the world, learning a variety of skills.
He wears a helmet connected to his brain and central nervous system, capable of downloading any type of knowledge as if he was Neo. But even without it, he's more than capable in martial arts, tactics, and intimidation, much like Batman himself. The sheer amount of ways that players would have to adapt to a villain capable of the amount of knowledge as the hero himself could make for one truly epic fight.
King Snake - Another consummate martial arts master, Edmund Dorrance was a former soldier of the British Army turned mercenary. At one point, he manages to take control of Gotham's Chinese triads, which could make him a possible subordinate of Black Mask's, or a potential usurper.
He also employs a mastery of stealth, which could make for a very intriguing boss fight against Batman. Furthermore, as the father of Bane. Snake's inclusion could make for an interesting look at a younger version of the muscled monolith.
Ubu - The bodyguard of the League of Assassin's Ra's al Ghul, Ubu is more of a title than that of a character, having been held at one time by Bane. This leaves Warner Bros. Montreal with an open template, leaving them to do almost whatever they liked with the character.
But more importantly, his introduction also serves as a great way of introducing the League.
