All Baton Pass related mons were unranked except for Scolipede, because Scolipede has a usable Waterium Z Set outside of Baton Pass. The same applies for Necrozma, who is incredibly dangerous with the following Set:
Necrozma @ Leftovers/Psychium Z/Pecha Berry
Ability: Prism Armor
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Iron Defense
- Calm Mind
- Stored Power
- Moonlight
With Scarf Dugtrio you can trap all relevant Dark types (except MSab). Aerial Ace also heavily weakens Mega Heracross, who is a problem because of the 5 hits Pin Missle critrate. If you want to be sure, you can use something like Eject Button Toxapex. The only way to deal with this mon after your hard hitters got trapped is Toxic, early Trick, early Haze or Hax. That is why you can use alternative Items like
a) Pecha Berry (+Tapu Fini Misty Terrain to be sure :D )
b) or Psychium Z.
With a Pecha Berry you can avoid any forms of Poison once which can be game deciding. Necrozma does not really care abt Burn dmg and while paralysis is annoying, there are no common paralysis inducing moves in SM OU. The only thing that comes close is Discharge from Zapdos.
A solid strategy to stop a Necrozma sweep is going hard Toxapex and to click Haze. A +1 60 Basepower Stored Power can be stalled out by Toxapex with Recover+Haze. With Psychium Z you can kill even max Spdef Toxapex with +1 Z Stored Power:
+1 0 SpA Necrozma Shattered Psyche (160 BP) vs. 252 HP / 252+ SpD Toxapex: 356-420 (117.1 - 138.1%) -- guaranteed OHKO
Another good thing is you do not have to fear any Tricks early game and Knock Off damage is heavily reduced
While Necrozma was C when Baton Pass was usable, I think it actually deserved a rank somehwhere in the Bs back then. Some replays with Necrozma after Baton Pass ban:
http://replay.pokemonshowdown.com/gen7ou-584238533 Easy Turn 1 sweep against Rain.
http://replay.pokemonshowdown.com/gen7ou-584669611 Turn 17 Band Zygarde attempts to Poison me. Pecha Berry comes in handy
http://replay.pokemonshowdown.com/gen7ou-584227232