Butterfree, at a glance, is a terrible Pokemon. Horrible typing, bad stats overall, a shallow movepool, and a 4x Stealth Rock weakness undermine much of her remaining positive qualities. However, Butterfree does have one thing going for her: a 97.5% accurate Sleep Powder! Compoundeyes remedies Sleep Powder's otherwise problematic accuracy, which plagues other sleep-inducing leads such as Scarf Venusaur and Jumpluff. Having access to a 97.5% accurate Stun Spore is also pretty good, and with U-turn to scout for switch-ins, Butterfree starts to seem like a decent option. In the end, while these things certainly don't make up for Butterfree's large number of shortcomings, they at least help her to stand out as an interesting alternative status spreader.
This set allows Butterfree to outspeed many Pokemon in UU and quickly cripple them with an accurate Sleep Powder or Stun Spore. This set functions best as a lead, since there is no need to worry about switching into Stealth Rock; she can also stop the opponent from getting up entry hazards, which helps her teammates later in the match. Even though Choice Scarf may lock you into Sleep Powder or Stun Spore, it is still Butterfree's most consistent way of spreading status, as Butterfree's frailty and relatively low base 70 Speed really hurt her ability to status things.
Sleep Powder is a given on this set, as the main reason you should be using Butterfree in the first place is her very reliable 97.5% accurate Sleep Powder. It's also (as mentioned previously) a great way to stop your opponent's lead from getting entry hazards up. U-turn provides a way for Butterfree to scout the opposition for any Sleep Talkers who may attempt to absorb your Sleep Powder, while Stun Spore allows Butterfree to accurately spread paralysis that's only blocked by Ditto, Persian and Hitmonlee later in the match. Bug Buzz rounds off the set by providing a nice STAB move from Butterfree's decent base 80 Special Attack.Team Options & Additional Comments >>>
Though this set seems extremely similar to the first set, it plays quite differently. Whereas the first set is guaranteed to put a Pokemon to sleep, this set attempts to cripple more of the opponent's team after you've slept the opposing lead, or provide a free switch-in to one of your Pokemon. This set is especially effective against slower leads such as Omastar and Uxie because Butterfree will be able to outspeed and put them to sleep, allowing her to either paralyze the switch-in if they switch out, or simply scout the opponent's move with U-turn. Against faster leads with Taunt, this set does much worse, as it is almost forced to U-turn immediately. However, this can still give one of your Pokemon a free switch-in, so this can potentially benefit your team.
Like the first set, Sleep Powder is once again used to stop slower leads from getting their entry hazards up. Stun Spore, with correct prediction, can allow you to cripple a third of your opponent's team in tandem with Sleep Powder via the Double Powder strategy. However, this strategy can be easily telegraphed due to it being commonly used on Butterfree, so U-turn provides a safe scouting move when you're unsure if your opponent will switch out. Protect is yet another scouting move that also allows you to stop the most common lead in UU, Ambipom, from breaking Butterfree's sash with Fake Out and KOing her the next turn.Team Options & Additional Comments >>>
Unfortunately, Butterfree's movepool is really shallow, so there aren't many viable options here. Roost and Morning Sun may be used if you want some healing, but 50% healing generally doesn't mean much for Butterfree. It could work somewhat decently if you're running a spread of 248 HP / 8 Def / 252 Spe, but even then, Butterfree is rather frail. Butterfree could cobble together a Sunny Day set up set with Sleep Powder, Sunny Day, Morning Sun/Safeguard, and U-turn, but other Pokemon can do a better job of it. Energy Ball can be used if you want to deal with Kabutops, Omastar, and Rhyperior; however, Bug Buzz is generally the better option, as you hit Mesprit and Uxie harder, both of whom are more common than Kabutops, Omastar, and Rhyperior. It should also be noted that even Energy Ball won't OHKO Rhyperior and only has a slim chance of OHKOing Omastar.
Checks and Counters
Butterfree absolutely despises any kind of Sleep Talker, as they can absorb the status effects, especially sleep, that Butterfree spreads around. RestTalk Altaria, Spiritomb, and Rotom are all particularly annoying for Butterfree to face because they can either set up in her face or, in Rotom's case, KO Butterfree with a STAB Discharge or Thunderbolt. Pokemon who can set up Substitute before Butterfree can do anything are also irritating for Butterfree to face, though they must be wary of Stun Spore on the switch-in. Rotom and Mismagius are great examples of this, as they're bulky enough to take Butterfree's weak STAB moves and set up on her.
As a lead, Butterfree fears Electrode. Electrode will always outspeed Butterfree and stop her from putting it to sleep with Taunt. From there, Electrode can set up Rain Dance without much fear of any of Butterfree's weak attacks. Leads with Lum Berry are also irksome, as the Lum Berry will remove the sleep instantly while the opposing Pokemon sets up on or KOes you. Lead Swellow is another lead who Butterfree fails against. With Protect, he can stop any attempts by Butterfree to paralyze or sleep him, then become immune to her status attacks via his Toxic or Flame Orb. After this, Swellow can simply KO Butterfree.
If you lack a Sleep Talker, sending a bulky Pokemon who can survive being asleep for a couple of turns will do just fine. Milotic, Registeel, Chansey, and Altaria are great choices for this. In the case of the last two, they can remove the sleep upon switching out with their handy Natural Cure ability, so they won't have to stay asleep for long. For Milotic and Registeel, they are easily bulky enough to sleep for a couple of turns and still take a few hits safely. Toxic Orb Clefable is also a good counter to Butterfree, as she becomes immune to Butterfree's status after Toxic Orb activates and can easily shrug off her weak attacks.