Warning! Spoilers for Dark Nights: Death Metal #1 below.
The DC Comics Universe has descended into chaos and calamity, as the Batman Who Laughs and Perpetua have shaped the Earth into their own image and shrouded it in darkness. The world's only hope against a full takeover from the Dark Multiverse is the last remaining heroes, who are scattered across the planet and beyond under the control of the evil Batman. One hero is about to get the last laugh, however, as Wonder Woman just took out DC's biggest villain.
In Dark Nights: Death Metal #1 from Scott Snyder, Greg Capullo, Johnathan Glapion, and FCO Plascencia, the Batman Who Laughs (under the command of cosmic god Perpetua) has taken over the world. Earth's remaining heroes have been largely split up, with Wonder Woman and Swamp Thing operating out of Hell, formerly Themyscira, Batman controlling his own undead army, and Superman on Apokolips after nearly succumbing to the Anti-Life Equation. However, once a weakened Wally West (with the powers of Dr. Manhattan) shows up as a prisoner in Hell, he tells Wonder Woman that Perpetua is being powered by crisis energy from the Dark Multiverse and the heroes are being kept alive to keep the crises going.
During Wonder Woman and Wally's conversation, the Batman Who Laughs shows up and promises that if she continues to play her part that she will be given her own safe planet with all of the remaining heroes currently held on New Apokolips. The Batman Who Laughs arrogance leads to him getting close to Wonder Woman, who pulls out the Chainsaw of Truth and kills the villain.
The news sends the Batman Who Laughs Batmen in a panic. Readers are immediately taken to a scene where a twisted version of Batman reveals their leader is dead. He tells the Jokerized Robins that they were Batman Who Laughs favorites before the villain's true plans are initiated. The Batman presses a Watchmen-esque button (with a frowny face, naturally) and calls for "the final Bruce Wayne," as a shadowy figure (with Dr. Manhattan's symbol on his head) emerges from the shadows.
Ultimately, Wonder Woman killing the Batman Who Laughs might have set his plan into motion much earlier than he anticipated. There's no telling what the "final Bruce Wayne" is capable of, but there's little doubt he's going to be an extremely powerful force for Perpetua and the remaining evil Batmen. With the Batman Who Laughs seemingly defeated, Wonder Woman can now launch her own counter-attack and reunite the last survivors of the Justice League to take down the Dark Multiverse for good.