Venomoth

Shield Dust
Secondary effects won't occur.
Tinted Lens
Doubles damage on resisted hits.
Wonder Skin
Reduces the accuracy of a status move to 50%.
Type Tier
Bug / Poison BL2
Level 100 Statistics (see level 5, 50, 100)
Min- Min Max Max+
HP
70
- 281 344 -
Atk
65
149 166 229 251
Def
60
140 156 219 240
SpA
90
194 216 279 306
SpD
75
167 186 249 273
Spe
90
194 216 279 306

Overview

Despite its BL2 status, Venomoth is an extremely potent Pokemon when used correctly. It's often thought that Venomoth is a high-risk / high-reward Pokemon, but this isn't exactly the case, as it's more along the lines of a mid-risk / very high-reward. It doesn't need in-battle support to work properly, just the right teammates so it can support them instead. And while it will absolutely wreck you if you underestimate it, don't overestimate it either, because it isn't all that easy to use due to its lack of bulk, which makes it hard to set up and restricts teammate options.

Name Item Ability Nature

QuiverPass

Black Sludge Wonder Skin Timid
Moveset EVs
~ Quiver Dance
~ Baton Pass
~ Sleep Powder
~ Bug Buzz
248 HP / 8 Def / 252 Spe

This set is meant to set up as many Quiver Dances as possible and then Baton Pass to a teammate to have them sweep. Sleep Powder makes this pretty easy, but be sure to not use it too early, or you might find it hard to get the actual pass off. The ideal situation to set up is when your opponent is in a situation where he can't hurt Venomoth (such as being Choice-locked into a Fighting-type attack or having a weak wall out), Quiver Dance on the switch (unless they have a faster Choice Scarf user, in which case you will need to predict a bit), then use Sleep Powder or Quiver Dance, depending on what came out, then Sleep Powder or Baton Pass. Don't get too greedy though, as a short sleep will mess up the strategy. You should be using Baton Pass right after Sleep Powder most of the time so as to maximize your chances of getting a successful pass off. Bug Buzz is mostly useful when Venomoth is up against a Roar user and has already used Sleep Powder. Wonder Skin will let it avoid Roar 50% of the time, so it has a good chance of outright beating them and then passing.

Team Options & Additional Comments >>>

Other Options

Venomoth can also take a slightly more offensive route and try to sweep itself by using Substitute over Baton Pass and Tinted Lens over Wonder Skin with either an offensive or defensive EV spread. An even more offensive set that takes full advantage of Tinted Lens with Life Orb and a fully offensive spread is possible, but you're usually better off using something else if that's the case, such as Lilligant or Rain Dance Kingdra, as Venomoth is usually a bit too weak to pull off sweeps this way. Another interesting option is Substitute / Disable / Quiver Dance / Bug Buzz with Tinted Lens, as this set will really mess with people who rely on Choice Scarf users to take on Venomoth.

Checks and Counters

This part's really tricky. Between Sleep Powder and its ability to boost its Speed, there is almost no way of ensuring Venomoth won't get a successful pass off. The only 100% sure way of preventing Venomoth from doing its job is by carrying two Choice Scarf users faster than Venomoth that can OHKO it. That isn't what I'd call effective teambuilding, though. Usually you have to predict around the Sleep Powder, ensuring your faster Choice Scarf user isn't hit by it and can get in before Venomoth gets to +2. Examples of such Pokemon are Darmanitan, Victini, Mienshao (which risks missing with Stone Edge), and Flygon (which needs Stealth Rock to OHKO). You can also deal with it by predicting the thing what it's going to pass to and try to OHKO it on its way in, but this isn't exactly reliable.

Other answers include Xatu, which bounces back Sleep Powder, has Psyshock to OHKO, and can Thunder Wave or U-turn out of the receiver as it comes in, giving you momentum. RestTalk Snorlax has a small chance to break up the play and doesn't really care about being asleep. Choice Band Sleep Talk Crobat is the perfect sleep absorber and can OHKO with either STAB move, but it's slower after a Quiver Dance and risks picking U-turn with Sleep Talk even if it somehow gets in before the Quiver Dance. The same goes with Choice Specs Sleep Talk Yanmega. Honestly, you're better off just discouraging Venomoth from setting up by playing smart and double switching a bit and/or hoping for a short sleep or Sleep Powder miss; that's how hard it is to stop Venomoth once it's in a position to set up.