If you loved Justice League: The Flashpoint Paradox, try Batman: The Dark Knight Returns, Part 2
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

Justice League: The Flashpoint Paradox
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Batman: The Dark Knight Returns, Part 2
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 Justice League: The Flashpoint Paradox, the second film will land in a comparable space — through a different lens.
dread
What Batman: The Dark Knight Returns, Part 2 is
Gotham City streets at dusk, sirens blaring, a bat-symbol shines bright. A weathered Batman faces off against a rejuvenated foe, the government intervenes with Superman. Jay Oliva renders the caped crusader's stubborn resolve.