What Pokémon can check Dusk Mane Necrozma?
While Necrozma-DM's typing lets it blanket check a large number of threats, it also leaves it vulnerable to very common threats in the tier, such as Primal Groudon, Ho-Oh, Mega Gengar, Yveltal, and Marshadow, due to its common weaknesses to Dark, Fire, Ghost, and Ground.
Source: Smogon's page on Dusk Mane Necrozma. I am not aware if all of these are available in the newest meta, I know Mega Gengar isn't, but the others should still hold true for Gen 8 if applicable.