OshyHikari
c l a r i t y
I beat it by using Zoroark disguised as mimikyu along with a toxic and foul play. Foul Play uses the boosted stats as damage against the victim.
Necrozma and those jacked up totem stats? It's easy to take on with 1 toxic and 3 foul plays and he doesn't know why his Light That Burns The Sky isn't working. Toxic gets worse and Foul Play does huge damage by itself.
I didn't use Zoroark though. I had to rely on my Magnezone's hefty load of resistances. Thankfully it doesn't have much of an answer to Steel-types either.