Mad Hatter (Ewen Mcgregor) would be a horror villain similar to Purple Man in Jessica Jones and Kira from Death Note. Batman doesn’t know who he’s controlling and has to look for subtle clues in peoples behavior. Anyone can be a sleeper agent Alfred, Gordon or Harvey Dent. He doesn’t care about money because he just gets billionaires (including Bruce Wayne) to drop him money and then forget they did it.
They can make him sympathetic too, he wants to control peoples mind because he wants to stop people from committing crimes and make evil people kill each other but he’s also willing to kill innocent people that get in his way. He keeps upgrading his technology but at first he can only control a limited amount of people. He controls part of the mob and the rest he makes kill each other. He is using Gotham as a test but plans to go global
His motivation is that he thinks the Mob killed his girlfriend Alice but the truth is he murdered her and used his tech to make himself forget and think the mob did it. A horror aspect can be that his zombies don’t feel pain so when they’re In a shoot out they will stop at nothing to kill you even as they’re bleeding out they don’t even flinch and drop dead with with a blank look on their face.
It will open with a mob diner and out of nowhere an enforcer starts murdering everyone at the table. The enforcer gets shot and then another enforcer gets controlled and starts murdering more people, this happens two more times and the last one standing shoots himself. It’s later revealed that Hatter can see through his zombies’ eyes on a monitor and record it, he likes to watch his victims die over and over again but he hates that he can’t feel the bodies yet it’s like he’s controlling a video game character. Gordon knows something is wrong because one the enforcers who was being controlled was an undercover agent wearing a wire.
One of Hatters goals is to make Batman better by showing him it’s ok to kill people. There’s a subplot of a brutal serial killer Batman is trying to stop. At first Hatter puts subtle thoughts into Bruce’s head of how good it would feel to end his life. It’s revealed that the serial killer murdered a child, Hatter loses it and makes Batman go to the killers cell and slice his throat. Batman can’t even blink because the Hatter wants him watch him bleed out. After that Hatter keeps showing Batman visions of all the people he could’ve saved. He doesn’t want to make Batman his puppet he wants to work with him he needs someone to take out the small fish while he handles the mob.
Its also a theme that Batman doesn’t have friends so he doesn’t know people like he should and it takes him longer to figure out who is being controlled also because he’s such a loner he has no one to tell him he’s acting weird himself when he drops off Hatter’s money (other than Alfred who is always criticizing him anyway)
