I came up with the idea for a Batman-Themed Killer.

Killer Idea: The Tallymarker(Victor Zsasz)

A perverted killer, there’s nothing charming or eccentric about this wanton, knife-wielding serial murderer who stalks Gotham City. His only affectation: a fresh tally mark carved into his own skin for each new life he claims.

Backstory: Victor Zsasz was the head of his own international company and had amassed a large personal fortune in addition to his family's wealth. When he was 25, his parents died in a boating accident, sending him into a deep depression. Afterwards he saw that his life was empty, driven by desire, and that there was no point to his existence. While he was attempting to commit suicide by jumping from Gotham Bridge, a homeless man tried to assault him with a knife, after he refused to give him money. Instinctively grabbing the knife, Zsasz saw in the man's eyes that all life is meaningless and that nothing nor anyone matters. He then proceeded to stab the man to death as a "gift" for saving his life. Indiscriminate in his prey, body count was the only thing that mattered to Zsasz. He took pleasure in arranging the corpses of his victims in life-like poses before carving a mark for each of his victims into his own body. He saved a special spot for the Batman. Victor Zsasz is not a super-villain. He doesn’t wear a costume, he doesn’t have themed henchmen, he doesn’t leave clever clues for Batman to find. He needs no money and no fame. His only desire is to kill and kill and kill and kill and kill and kill. Every time he tried to kill the Bat, he was thwarted and sent to Arkham. There, every now and then, a super criminal from the maximum security wing would escape and Zsasz would too, killing all those he pleasured in his path. One night, after such a breakout, Zsasz heard whispers from the depths of the Asylum's lengthy halls. He didn't escape, but his cell was empty ever since.

Weapon: Combat Knife

-An old combat knife stained with the blood of the innocent.

Power: Marking Knives

You carry with you four smaller knives that can be thrown with deadly precision. Other knives can be found hanging on hooks. Hitting a survivor with those knives causes them to be afflicted with the Marked Status Effect. Survivors who are marked bleed profusely, but do not go into the injured state. This causes them to leave large pools of blood that can be sensed by you. Moving causes them great pain, and their Marked meter goes up. When the Marked meter reaches its peak, the survivor goes directly into the dying state and cannot recover from this for 120 seconds. You receive a notification when this happens. Another survivor can remove the knife by successfully completing a skill check, but the marked survivor screams when the knife is removed.

The Killer's Teachable Perks:

Perk 1: Perversion

Your weapon meeting Survivor flesh fills you with glee. For 120 seconds after hooking a survivor, your Terror Radius is reduced by 8/9/10% and you gain a 3%/4%/5% boost to your movement speed.

"It is you who doesn't understand. The beauty of death, the quiet voyage into the unknown, the escape from the misery of the ordinary. But you will."

Perk 2: Tolerant

You know how to deal with pain. Destroy pallets as you are being stunned(raises arm and smashes pallet), but stun duration is moderately/slightly/not increased.

"This won't end here. I will get out of here and continue my work."

Perk 3: Liberator

They don't know it's for their own good, but you do. Upon sacrificing a Survivor, all live Survivors' auras are exposed to you for 8/9/10 seconds and you become undetectable for 15/20/30 seconds.

"The zombie is mine to liberate!"

Give me more ideas in the comments on how to improve!