If you loved Batman: The Dark Knight Returns, Part 2, try Justice League: The Flashpoint Paradox
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

Batman: The Dark Knight Returns, Part 2
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Justice League: The Flashpoint Paradox
What they share
Both films are directed by Jay Oliva, and they both carry the dread mood tag, and they sit in Action / Animation / Science Fiction territory. If that's the register that drew you to Batman: The Dark Knight Returns, Part 2, the second film will land in a comparable space — through a different lens.
dread
What Justice League: The Flashpoint Paradox is
Central City, lightning storm, sirens blaring. A fractured timeline unfolds, alternate heroes assemble, and the Flash runs out of time. Jay Oliva brings DC's darkest animated corner to life.