Summary
Aquaman: The Lost Kingdom’s darkest death theory just came true in an even worse way in theDCmovieJustice League: Crisis On Infinite Earths Part Three. While one film was the live-action ending tothe DCEU timelineand the other is the animated finale tothe Tomorrowverse timeline, both releases have a fair amount in common - with the most obvious of these connections being that they ended their respective franchises.
Naturally, being the last releases in relatively extensive worlds placed a certain pressure on both films, with the stakes being raised even higher due to this detail. This combined with other factors led to one especially grim theory that arose forAquaman: The Lost Kingdom- and while this didn’t prove true for the DCEU movie, it wasn’t long beforeJustice League: Crisis On Infinite Earths Part Threemade it a tragic on-screen reality.

Aquaman: The Lost Kingdom’s Aquababy Death Theory Was A Truly Dark DC Rumor
Aquaman: The Lost Kingdomprominently featured Arthur’s son, Arthur Jr. - also known as Aquababy - who has a notable history in DC comics. Unfortunately, that history is notable because the child dies in the comics, having been killed by Black Manta. As such, theAquaman: The Lost Kingdomtrailers focusing around Arthur Jr. and Black Manta coming for revenge led audiences to fear the worst for the Aquaman adaptation, which would have been especially dire since the sequel was the final release in the DCEU timeline before its reboot into theupcoming DC Universe.
Mercifully, this turned out to not be the case for this film, with the DCEU version of the baby making it to the end of the movie more or less unscathed. However, a later DC installment still managed to bring an even more grim version of this storyline to screens.

Aquaman 2’s On-Screen Aquababy Death Theories Came True After The DCEU’s Ending
Justice League: Crisis On Infinite Earths Part Threesaw the destruction of billions of lives as entire planets were destroyed by the Anti-Monitor. A handful of these deaths were shown on-screen, in order to add weight and poignancy to the stakes at hand. Sadly, this included showing both Aquababy and his parents being killed by the destruction of their world, complete with a sad shot of Aquaman and Mera with their child before the Earth was wiped from reality.
Since this came after the DCEU dodged the Aquababy death theories, the scene feels even more shocking. Indeed, this is likely the purpose of the scene forJustice League: Crisis On Infinite Earths Part Three, as these sudden and jarring murders showcase the tragedy of the story effectively, and further explain why the remaining heroes are willing to do almost anything to ensure the entire multiverse isn’t destroyed bit by bit.

Justice League: Crisis On Infinite Earths Part Threealso seemingly destroyed the DCAU and Super-Friends show universe, though it’s unclear to what degree this is to be considered universally canon across all of DC.
Why Crisis In Infinite Earth’s Aquababy Death Is Even Darker Than The DCEU Theories
Not only was theJustice League: Crisis On Infinite Earths Part Threescene arguably worse than the DCEUAquaman: The Lost Kingdomtheories because it came out of left-field, it also comes across as darker because Aquababy’s death came with an entire world’s destruction. As such, Aquaman and Mera didn’t even get time to process or grieve this tragedy, since the family all passed alongside their home at the same time.
While this version of Aquaman did return home to his partner and child to die alongside them, this also actively makes the situation even sadder. Ultimately, the hero was forced to make an unbelievably awful decision in terms of either leaving his family to their fate without being there or going back to face certain death, making his fate a remarkably grim one.

The lack of time to deal with or even comprehend this scenario underlines just how hard this situation is for all of DC’s heroes, and using an innocent figure like Aquababy as an example of how ruthless the Anti-Monitor is and how dire the circumstances are appears to have been the intent of the movie.WhileJustice League: Crisis On Infinite Earths Part Threeends with the multiverse being reborn into the Prime universe, it can’t be said this process was an easy one, and such tragic moments exemplify that idea.
Justice League: Crisis on Infinite Earths - Part Three
Cast
Now fully revealed as the ultimate threat to existence, the Anti-Monitor wages an unrelenting attack on the surviving Earths that struggle for survival in a pocket universe. One by one, these worlds and all their inhabitants are vaporized! On the planets that remain, even time itself is shattered, and heroes from the past join the Justice League and their rag-tag allies against the epitome of evil. But as they make their last stand, will the sacrifice of the superheroes be enough to save us all?