Both movies deal around a natural catastrophe that set the world into chaos. In both dramas the characters have to find a way to survive. The only difference is that Ashfall revolves around a volcanic eruption while The Calm Beyond focuses on tsunami due to a storm.
The Calm Beyond (2020)
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It is thriller and type of survival. I have only seen the trailer of this movie, but you would probably like this series if you like thrillers…
Watching one reminded me of the other. Both take place in a dystopian world where each has to survive. While The Calm beyond focuses on a natural catastrophe and the aftermath of it, Alice in Borderland pulls the people into a game.