Why Batman became Batman Who Laughs?
By killing the Joker, Batman accidentally breathed a toxin within the villain's body, which slowly rendered him insane and transformed him into the very same thing the Joker was: a nihilistic mass murderer, who became known as The Batman Who Laughs.
Targeting members of the Justice League and their allies, the Batman Who Laughs used special Batarangs coated with the same toxin that the Joker used to initially infect him to infect four heroes to his cause: Shazam, Hawkman, Donna Troy and Blue Beetle.
Bruce has always feared that something, or someone, would push him to a place where he would become the very things he detests. The Joker has long been the embodiment of everything Batman hates most. Yet he cannot destroy him because it would mean crossing a line from which he could never come back.
DC Declares the Batman Who Laughs a New God With Death Metal One-Shot. The Batman Who Laughs is now more powerful than ever, and a tie-in special to Dark Nights: Death Metal will expand on his rise to godhood.
The Batman Who Laughs is a version of Batman from Earth -22 of the Dark Multiverse. In that reality, the Earth -22 Joker learns of Batman's identity as Bruce Wayne and kills most of Batman's other rogues, along with Commissioner Gordon.
During the events of Dark Knights: Death Metal, The Batman Who Laughs gains the powers of Dr. Manhattan by having Dr. Arkham surgically integrate his mind into that of a Bruce Wayne with Manhattan's powers, granting him nigh-omnipotence, flight, and teleportation among other powers.
To begin with, The Batman Who Laughs is changed because of the Jokerized poison gas. Because of this, his eyes can see through the membrane of the multiverse.
This Batman Who Laughs is based on the character's later appearance after he steals the wings from the Sky Tyrant, the Dark Knights Metal version of Hawkman.
Invisible Woman Would Take Down The Batman Who Laughs With Little Trouble. The Invisible Woman is the most powerful member of the Fantastic Four and it's not even close. Turning invisible is just the beginning of her powers.
As we've seen in Snyder's Justice League, the Joker hates the Batman Who Laughs. The Joker's disgust for the BWL is even part of how he was defeated in Dark Nights Metal. But The Batman Who Laughs #4 shows that this isn't your usual supervillain rivalry about how only he gets to kill Batman.
What is Batman's deepest fear?
Wayne's phobia of bats is the most apparent. It stems from his childhood incident of falling down a well with bats flying up above him. Because the incident happens at such an impressionable age, it causes extreme fear and becomes impossible to get rid of.
He's a creepy nightmare that even the Joker is afraid of. And for good reason, since the Batman Who Laughs is basically the skill and tenacity of Batman mixed with the chaotic evil of the Joker.

With such a powerful foe in Barbatos' corner and a Bruce Wayne who can predict Batman's every move, Batman had to throw a wild card into the ring in order to gain the upper hand. He did what many might believe to be unthinkable. He teamed up with Joker in order to defeat the Batman Who Laughs.
He uses a visor made of dark metal to filter out the dark energy and noise in order to focus on what he wants to see. This visor is spiked and would appear to blind him if it wasn't for the knowledge that it actually helps him see.
Batman took advantage of the Flash's compassion, using it to knock him out before strapping him onto the Batmobile to tear open the Speed Force. The resulting drive through it merged Barry and Bruce, transforming them into the Red Death.
Invisible Woman Would Take Down The Batman Who Laughs With Little Trouble. The Invisible Woman is the most powerful member of the Fantastic Four and it's not even close. Turning invisible is just the beginning of her powers.