Nice calculations on Necrozma - Dawn Wings! What tier in Ubers do you think Ultra Necrozma will be at? I think S tier!Alright I've decided to be a masochist and attempt to work the loser of all this, Necrozma-DW. I guess you can use it to pass Moongeist onto Ultra, or fake a special set then Swords Dance + Ultra (you'd be really desperate to do this), but I'm gonna talk about the vanilla forme. Basically it has approximately two things over Lunala - Rock Polish and Stealth Rock. Rock Polish may be a tall order due to its lack of coverage and vulnerability to SSneak/Sucker, but Stealth Rock might get us somewhere...
Necrozma-DW @ Lunalium-Z
Ability: Prism Armor
EVs: 4 Def / 252 SpA / 252 Spe
- Stealth Rock
- Calm Mind
- Moongeist Beam
- Power Gem / Psyshock / filler??
Necrozma-DW has a matchup advantage against every anti-hazard Pokemon except for Defog Arceus-Dark and possibly Yveltal. Being part Ghost also enables it to block Rapid Spin (you might want to consider running more phys bulk to not get 2HKOed by Excadrill EQ maybe?), although that'd more relevant a few generations ago. Calm Mind makes it possible for Necrozma-DW to blast through bulkier threats such as Ho-Oh, Primal Kyogre, and various support Arceus formes. You probably won't get a lot of set up turns but it makes sure your opponent can't play passively. Last slot is kinda filler bc I don't really know what to put in there. Power Gem's your best bet at hitting Yveltal (and Ho-Oh w/o Z moving it) while Psyshock's for blobs I guess.
Additionally, Necrozma-DW has a positive matchup vs some bulky SR setters such as Primal Groudon, Dialga, and Arceus-Fairy. Hit X if you face a TTar though.
Oh as a bonus it checks Necrozma-Ultra to an extent
EVs are pretty arbitrary but I'm sure there's room to give it actual modifications
252+ SpA Necrozma-DW Moongeist Beam vs. 0 HP / 4 SpD Giratina-O: 410-486 (92.9 - 110.2%) -- 56.3% chance to OHKO
252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 252 HP / 0 SpD Dialga: 414-487 (102.4 - 120.5%) -- guaranteed OHKO
252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 252 HP / 0 SpD Arceus-Neutral: 354-417 (79.7 - 93.9%) -- guaranteed 2HKO (just CM. Also does roughly the same to max/max+ Primal Groudon)
252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 252 HP / 0 SpD Mega Salamence: 451-532 (114.4 - 135%) -- guaranteed OHKO
252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 248 HP / 44 SpD Celesteela: 391-462 (98.4 - 116.3%) -- 87.5% chance to OHKO
252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 252 HP / 232+ SpD Mega Sableye: 274-324 (90.1 - 106.5%) -- 43.8% chance to OHKO
(don't worry Foul Play doesn't OHKO you)
+1 252+ SpA Necrozma-DW Menacing Moonraze Maelstrom vs. 252 HP / 0 SpD Ho-Oh: 424-501 (101.9 - 120.4%) -- guaranteed OHKO
In other words if you don't have a Ghost resist this mon can probably set up rocks and punch holes. It can get hardcountered pretty easily with certain tools but otherwise you might actually have to respect it. That said its lack of a defensive typing will make it awkward to fit into teams.