NFE Defensive Double Dance (Duosion) @ Eviolite  
Ability: Magic Guard  
EVs: 248 HP / 196 Def / 64 SpD  
Calm Nature  
IVs: 0 Atk  
- Acid Armor  
- Calm Mind 
- Recover 
- Psyshock
Optional Move(s): 
- Hidden Power [Fighting]
- Hidden Power [Ground] 
- Psychic
- Shadow Ball
- Signal Beam
- Trick Room
Optional Item(s): 
- Focus Sash
- Life Orb
Optional Ability: 
- Overcoat 
Optional EV/IV(s): 
- 252 HP / 252 SpA / 4 SpD (Quiet)
Overview: Duosion functions as a bulky late-game win condition. With good bulk, Magic Guard and access to both Acid Armor and Calm Mind, Duosion is one of the best bulky setup Pokemon in the metagame. However, it is completely walled by Dark-type Pokemon. 
Defensive Double Dance: Magic Guard is a fantastic ability for bulky setup Pokemon like Duosion, since it negates all hazard damage and status chip from Toxic or Burn. Duosion can boost its Defense with Acid Armor and set up on physical attackers such as non-Flame Orb Machoke, Sliggoo, Staravia and Metang. Calm Mind lets it boost its Special Defense and Special Attack and set up on special attackers such as Choice Specs Thunderbolt Electabuzz, non-Encore Kadabra and Roselia. It can also set up on more passive Pokemon such as Prinplup, Ferroseed and Gloom. Recover lets Duosion recover its health which enables it to set up on and outlast opposing Pokemon. Psyshock is Duosion's only STAB attack and it hits a majority of the tier hard after a few Calm Mind boosts. Psyshock also beats other Calm Mind setup Pokemon such as Clefairy.
Checks & Counters: Dark-types such as Alolan Grimer, Krokorok, Pawniard and even Protean Dark Pulse Frogadier completely wall Duosion and hit it with super effective damage. Alolan Grimer can Clear Smog all boosts away and Pursuit trap it, while Pawniard can outboost it with Swords Dance. Haze users like Dusclops can also remove all boosts from Duosion and stall it out with Pressure and Seismic Toss or force it to switch. Servine can switch into Duosion and outboost it with Contrary Leaf Storms. Encore and Taunt users such as Kadabra, Quilladin and Torracat can either lock Duosion into a setup move or Psyshock which typically forces Duosion out of the field.
Optional EV/IV(s): An alternative spread of 252 HP / 252 SpA / 4 SpD with a Quiet nature is used with the Trick Room set.