While The Flash will be a similar multiversal epic to Marvel's Spider-Man: No Way Home, the upcoming DC movie from Warner Bros. will have much larger and far-reaching consequences. Mirroring the Flashpoint event from the original comics, Barry Allen will attempt to save his mother in the past, an act which inadvertently changes the entire timeline and leads to a collision of worlds within the DC multiverse. As such, the circumstances of The Flash will lead to a far more significant ending than No Way Home's.
It's already been confirmed that The Flash will feature two different Barry Allens as well as two different versions of Batman, one played by Ben Affleck and the other by Michael Keaton from the Batman movies directed by Tim Burton. As such, the comparisons to Spider-Man: No Way Home have already begun seeing how the MCU's Peter Parker joined forces with Andrew Garfield and Tobey Maguire's respective takes on the iconic Wallcrawler. However, the ramifications of The Flash and its ultimate conclusion will be far more significant.
