My whole life, I had been afraid of doing what I knew needed to be done. Afraid to give all of myself to the battle. The helmet showed me that my codes and rules were naive. That all that truly mattered was victory. And now I would finally take it for myself.
~ The Merciless
I look at him and see the man I used to be. He fights with mercy. With restraint. Which is why he'll lose. And this world will fall to Barbatos.
~ The Merciless.
The Merciless is a villainous version of Batman from the DC Comics universe. He is a member of the Dark Knights, a group of vigilantes from the Dark Multiverse whose goal is to assist the deity Barbatos to plunge the central DC Multiverse into darkness.
On Earth -12, the God of War Ares managed to create a helmet that amplified his powers a hundredfold. After learning of this, Batman and Wonder Woman vowed to slay the god and destroy his helmet.
The pair got embroiled in a 2-year-long war against Ares' forces before finally confronting the deity in combat, during which Wonder Woman was seemingly killed. Heartbroken over losing the woman he loved, Batman swore Ares would pay then used the God of War's helmet to kill him, although it's power corrupted Batman's mind in the process. Afterward, Batman found that Wonder Woman was still alive and had just been stunned by Ares, but when she tried to remove the helmet from him, Batman chose to kill her rather than give up its power.
The empowered Batman then dropped his moral code and went on a killing spree; murdering various criminals and later heroes who tried to stop him. Eventually, Batman's rampage took him to Olympus as Earth -12 began to collapse, and was then given an opportunity by The Batman Who Laughs to take part in "the greatest war the cosmos has ever seen"; a war of survival. Wanting to prove that his new philosophy is the correct one and having nothing left to lose, Batman took up his counterpart's offer and joined the Dark Knights as The Merciless.