Prim's usage went up in Snake from 2 teams to 4, and I think that's awesome, because she hits stupidly hard. Specs Hydro 2HKOes Celesteela and OHKOes a bunch of other stuff. Boots is very reliable, as Prim already has a high SpAtk stat anyways and doesn't need to rely on boosts or items too much, and Sub CM once it gets going is unstopabble, but I do prefer the raw power of Specs. I've seen Lilburr and Adaam talk about Primarina and how good it is, and I agree. I wish more people would use it, just for the raw power of the specs set. Flip Turn is also an option on specs, so you can capitalize on forced switches even more. Psychic coverage hits its 2 best checks in Amoon and Tenta too.
Amazing mon rn. Very versatile, has great typing and access to SR. I think the best sets rn are defensive and offensive rocker. Defensive checks a lot of stuff, like Victini, Crawdaunt, Zeraora, Lycan-D, both Rotoms, Bulu, Volcanion, etc. What makes Kommo-o good but not absolute best is that, out of all those mons I listed, only one doesn't have a way of dealing with it, which is Crawdaunt, as CC just doesn't cut it, even on CB sets. Tini can run Zen Headbutt or mixed sets, Zera has Play Rough, Lycan can run Psychic Fangs (which also hits Nidoqueen), Rotoms have space for Toxic, banded Bulu can do a good chunk with Zen Headbutt and Volcanion can overpower Kommo-o with a specs set. Still, Kommo-o manages to be a very good defensive mon and def worth using. Offensive can scare Scizor with Flamethrower, Primarina with Poison Jab, and defensive Mence with Dragon STAB, while it has the opportunity to set Stealth Rock too.
This one I've seen quite a bit. Double Dance is an actual threat, as at +2 on both Speed and SpAtk, there's not much outside of priority that can deal with this. Its defensive typing isn't the best and its main role as an Aegi check is now gone, but Dark/Flying is a good offensive typing. Under screens, this thing is almost unkillable in even 2 hits and once it gets the Berserker boost after a NP... scary. Still not overwhelming tho, but I always have to play careful as to not give it free turns to setup, because once it gets going, good luck.
One of my favorite mons to use, very very fun! Meteor Beam Power Herb is a nice combo and if you get rid of its checks, it can sweep pretty easily. Scarf saw more use when it first dropped, and now I haven't really seen much of it, but it's still very very good. Stealth Rocks / Toxic Spikes + 3 attacks is also very fun to use, because Nihi does force a lot of switches due to good offensive typing. However, Nihi does suffer a lot from both the loss of Hidden Power and from 4MSS in general. It needs to run one of Meteor Beam/Stealth Rock/Toxic Spikes for its sets, meaning one slot is gone (and the scarf set generally runs power gem/sludge wave/tbolt/filler, so power gem just replaces meteor beam). Next comes Sludge Wave to deal with Fairies and stuff like Kommo-o, Latias, Amoong, and Rotoms. Then you run Tbolt for Steela and Tentacruel. You are then left with Dazzling Gleam, which imo isn't worth it at all, only hits Kommo-o. Psychic can also work for Amoong and Nidoqueen, but then that's it, really. Grass Knot still doesn't do a lot to Nidoqueen and Mamoswine. Not to mention you want to run Power Gem to hit Salamence, Victini, Rotom-H, and Volcanion more reliably. And with all that coverage, Magnezone, Scizor and Jirachi STILL wall you to no end. Priority and laughable physical bulk also make Nihilego easier to deal with. Despite all this, Nihilego is a very good mon, not to mention it being a healthy presence in the tier, keeping dangerous threats like Thundurus-T in check.
Gonna mention these 4 in the same paragraph because I think they're extremely underrated. Kyurem's coverage is AMAZING, and very little stuff can check it, Steela and Scizor being the only ones I can think of right now. Granted, Steela is the most used mon in the tier, but we do have answers for it, and as soon as its gone, Kyurem just takes lives. Diggersby, on the other hand, doesn't care about Steela and just SDs as it comes in and Fire Punches it to oblivion. Not to mention priority Quick Attack and STAB EQ. Scarf sets can take you by surprise too! Durant hits stupid hard with Hustle + CB, and its priority although not spammable as Diggersby's, is way stronger and can cleanly OHKO foes. Steela keeps it in check too, but there's not really else. Amoong def doesn't want to take CB Iron Heads, nor does Cobalion want to take Superpowers, while Salamence doesn't like Stone Edge. Durant is just a good mon in general! Conk's Flame Orb set is GREAT, specially paired with Bulu, negating its recoil, and they also help each other by sharing checks and chipping them down for each other, like Steela, Kommo-o and Scizor. I haven't tried Bulk Up, but does seem to be nice, tho with Steela, Kommo-o, Latias, and Azu running around, I don't know if it has the same value. More people should use these 4, as they have great prowess as wallbreakers.
