This Dark Matter stuff is dumb, DM says he wants to "turn the world back to the void" or something like that, however the only way he can achieve its goal is to destabilize the planet so it is absorbed by the sun
Actually, that wasn't how he was doing it.
He was going to throw the Tree of Life into the Sun. When that happens, natural functions like the Planet spinning will fail and will destroy the planet.
But that's not how he's going to return All Creation to the Void. He doesn't say how he's going to return All Creation to the Void, and he doesn't say that throwing the Planet into the Sun is how he's gonna do it either.
I remember correctly he needed weeks or months to make progress (And he needed energy from the Tree of Life to even accomplish something that is not even comparable to erasing a universe, something that Dialga or Palkia can do without a problem.)
What do you mean?
Moving the Tree of Life is massively above Low 2-C. The Tree of Life is the Foundation for Life itself, which would include many Pokemon who are above Low 2-C like the Creation Trio, Lake Trio and Arceus themselves.
Also the creation trio are not even alive in a conventional way to begin with.
They are still alive though, even the profiles only give them Type 1 and 9 Immortality.
Even Arceus. So no there is no "But unbound from Life and Death, Type 5 Immortality" argument.
Do you have proof of that?
Yveltal is the counterpart to Xerneas, who is the embodiment of the Tree of Life and is the Tree of Life itself.
It follows as it's dual opposite it too is a conceptual being. In the game itself, it states that it is the True Destroyer and the End of Pokemon.
So he could just be that.
Also, you can't say that DM can destroy the canon Pokémon cosmology when elements of his own game prove that it doesn't even belong to the same cosmology/canon.
Not really, the Tree of Life existing doesn't contradict a single thing. It just means that Arceus made something else that binds him, just like his plates, just like the Jewel of Life.
Basically, you can't say that DM > Canon/2-A/B Arceus, when elements of SMD prove that SMD Arceus ≠ Canon/2-A/B Arceus.
But we can, and I've already explained how we can, SMD's elements don't contradict, you're just trying to nitpick the argument now and are trying to default to it not being canon entirely, which isn't very convincing.