Dawnbreaker was created by Scott Snyder and Greg Capullo. He made his first appearance in Dark Days: The Casting.
What makes Bruce Wayne of Earth-32 interesting, is the fact that he never became Batman to begin with. Bruce has lost his parents very much like Batman from the main earth. However, this time, the green power ring has chosen him (mere minutes after his parents were murdered) to be a successful green lantern. Due to Bruce's incredible willpower, he was able to overrule the ring's "lethal force not permitted" rule. In all his rage, he killed the murderer, thus allowing the ring (which is now corrupted) to consume him.
He goes on to take out each and every criminal (Scarecrow, Penguin, etc.) of Gotham by using lethal force. Gordon warns him that this needs to stop, this isn't the way, this isn't justice. Bruce doesn't care at all and disintegrates him with his ring.
The Guardians must have noticed what's been going on lately, as they arrive on earth with the entire GL corps. Without the slightest hesitation, he manages to murder all of them.
Dawnbreaker's infamous oath: With darkness black, I choke the light. No brightest day escapes my sight. I turn the dawn to midnight. Beware my power DAWNBREAKER'S MIGHT!
Powers and Abilities
Dawnbreaker is a bearer of the Green Lantern Ring and has all of the powers associated with it. His willpower was so great and the dark void of his mind so corruptible the ring malfunctioned and not only makes constructs of will but seeps the dark void out of Dawnbreaker's mind choking light with complete darkness and making dark creatures to attack with.