The title of this article is conjectural as this subject has no known canonical name in the DCEU.
The Injustice War was the lengthy conflict that occurred in a possible future, between Superman's Regime, and Batman's Insurgency, due to the latter wishing to overthrow the new tyranny. Superman would ultimately prevail, however, prompting that possible future's version of the Flash to warn a past version of Batman.
At some point in a possible future, either Lois Lane or Martha Kent would be killed, with Batman having been unable to prevent it. Superman, unhinged with grief, becomes dark and malevolent, taking over the Earth as its tyrant ruler, and founding the Regime Stormtroopers to aid him in his totalitarian Regime of Earth, mercilessly killing anybody who opposes him. Batman promptly founded the Insurgency in order to combat this new threat, thus beginning the long Injustice War.
Final BattleEditBatman, in desert clothing, exits a bunker, and watches his Insurgency allies approach. He meets with them and asks for the Kryptonite rock, the only remaining hope of defeating Superman. However, they open the box to reveal only green light bulbs. They apologize to him and hold Batman at gunpoint. He follows through with their commands as the undercover Regime Stormtroopers reveal themselves to Batman and the Insurgents. They execute them, as Batman watches helplessly. Angered, he begins a killing spree and guns down multiple stormtroopers, while helping some of his surviving Insurgents escape the area. Although he manages to take down most of the Regime Stormtroopers while Parademons invade the area and abduct many humans there, Batman is eventually overwhelmed by the remaining stormtroopers there who could barely restrain him. He snaps one of their necks, but then is brutally (but barely) beaten by the other stormtroopers. Seeing the damage that Batman was inflicting on the stormtroopers and their inability to restrain him, a Parademon knocks Batman unconscious.
Batman recuperates chained up in the bunker with his few remaining Insurgent allies, eyeing them helplessly. Superman himself then lands in the bunker, and his Regime Stormtroopers reverently kneel before their leader. He approaches Batman, swiftly murdering the other Insurgency members with his heat vision. Superman then unmasks the horrified and visibly scared vigilante. He expresses his anger at Bruce for letting "her" die, as she was "his world". Superman gives Batman one final sinister sneer, and ruthlessly kills him by tearing Batman's heart from his chest, thereby ending the Injustice War.
Batman, not believing this experience to be a dream, initially uses this as an extra justification and motivation in his quest to take down Superman. However, after Superman's death proves Batman's initial thoughts invalid, he finally heeds future Flash's warning, and requests Wonder Woman's assistance in founding the Justice League.