While Ben Affleck's Batman is confirmed to have a role in The Flash, an appearance from the Knightmare version of the Dark Knight could create closure for Zack Snyder's vision for the DCEU and for Bruce Wayne himself. Although Warner Bros. has drifted away from the future set up by Zack Snyder's Justice League, the upcoming film starring Ezra Miller's Scarlet Speedster could provide some closure before Barry Allen reboots the timeline as has been heavily rumored. Likewise, Barry meeting the Knightmare Batman could be the perfect way to say goodbye to the Snyder era of the DCEU.
First featured in the Snyder-directed Batman v Superman: Dawn of Justice, Bruce Wayne dreamed of the future where Darkseid has taken over the world and corrupted Superman, turning the Earth into an apocalyptic wasteland. Dubbed the «Knightmare Sequence», Batman is seen sporting a jacket, scarf, and goggles to protect him from the harsh elements, leading soldiers against parademons before being killed by the Man of Steel himself. Furthermore, Zack Snyder's Justice League featured a return to the Knightmare future which would have been the backdrop for Snyder's Justice League sequels. However, it doesn't look like that future will ever come to pass with Warner Bros. largely parting ways with Snyder.
Related: Why There Are 3 Batmans Now
Due to the rumors that The Flash will give the DCEU a soft reboot, it seems Snyder's vision will truly be no more once Barry Allen resets the timeline and creates a new reality (with Michael Keaton's Batman being teased as the new Dark Knight of the DCEU going forward). As such, it would certainly be significant if Ben Affleck's role in The Flash was the Knightmare Batman. Barry Allen could meet with this version of
Read more on screenrant.com