Felt like mostly a cash-grab.
First thing that caught my attention right away is that the animation and style in general felt a bit different from the previous movies and main TV show. Was not able to understand what exactly felt different, but I can say for sure that some comedic moments reminded me of older American cartoons somehow. Fights were not that interesting, because they were resolved by "I will just go faster or hit stronger", rather than with some smarts.
The story is even worse. It was essentially Eri's ark, but with hints of grooming and then kidnapping by another party. Anna's quirk is also kind of like Eri's, I'd say. Or at least very similar. It did not make sense that it was killing her even when she was "releasing" it, though, and I did not get how it would make quirks evolve infinitely when she loses control. What's more, since her touch does not kill, but only hurt, why didn't that butler guy try her compatibility right away? Why did not Anna's father suggest that? That's stupid.
Not to mention that this was extremely predictable, and "Dark Might" felt almost like Shigaraki, but without charisma. Which would make the actual fight with Shigaraki easy, since it's supposed to be after this. But we know it was not easy. As such this movie does not fit the lore as nicely as previous ones. Made just to parasitize on the fandom.
