NFE Nasty Plot Cleaner (Poipole) @ Eviolite / Poisonium Z
Ability: Beast Boost  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Nasty Plot  
- Sludge Wave  
- Dragon Pulse  
- Hidden Power [Fire] 
Optional Move(s): 
- Hidden Power [Ground]
- Substitute
Optional Item(s): 
- Dragonium Z
Optional Ability: 
- N/A
Optional EV/IV(s):  
- 252 SpA / 4 SpD / 252 Spe (Modest)
Overview: With access to both Nasty Plot and Beast Boost, an ability that boosts Poipole's largest invested stat by one stage each time it knocks out an opposing Pokemon, Poipole can act as a potent cleaner for mid- and late-game scenarios. However, awful coverage prevents it from being anything greater than a niche cleaner. 
Nasty Plot Cleaner: Nasty Plot boosts Poipole's Special Attack by +2. Sludge Wave acts as solid STAB attack and hits Fairy- and Grass-types, such as Servine, Clefairy, Quilladin, and Togetic, as well as frailer neutral targets, hard. Dragon Pulse acts as decent coverage move against Pokemon such as Gabite, Fraxure, and Alolan Grimer. Hidden Power Fire hits Steel-types such as Ferroseed, Pawniard, and Metang reasonably hard after boosts. If Timid, Poipole gets a one stage boost to Speed every time it gets a KO, making it more difficult for it to be revenge killed by faster attackers and Choice Scarf users such as Haunter, Monferno, and Frogadier. Poipole's pure Poison-typing lets it set up fairly easily on defensive Pokemon such as Clefairy, Roselia, and defensive Togetic, as well as weak attackers like Prinplup. The Eviolite set can tank a reasonably strong neutral hit, which lets it set up on a larger portion of the meta. The Z-Move set gives up bulk for a nuke attack against bulkier threats.
Checks and Counters: Specially defensive Mareanie and Dusclops can switch into Poipole easily, Haze away any accumulated boosts, and wall it. Specially defensive Alolan Grimer also takes very little from boosted Dragon Pulse and can Clear Smog away boosts or hit it hard with Knock Off. Bulky Steel-types like Metang and Klang can tank a +2 Hidden Power Fire and either revenge kill or hit Poipole hard in return. Focus Sash Kadabra can exchange its Focus Sash in order to revenge kill a boosted Poipole. Choice Scarf users faster than 403 speed such as Krokorok, Monferno, Staravia, and Frogadier can usually revenge kill +1 Poipole from full or after some chip.