CT Chia
Smash Obsessed

#012 Butterfree
Typing: Bug/Flying
Ability: Compoundeyes- Increases this Pokémon's Accuracy by 30% and increases the chance of finding items on wild Pokémon.
60/45/50/80/80/70
Chibofree
Butterfree @ Focus Sash
Modest/Compoundeyes
252Spe/252SAtk/4SpDef
-Sleep Powder
-Dream Eater
-Tailwind
-Bug Buzz
I can't think of a better name for this pokemon -_- so I'll stick with Chibofree. It's a set I made up for it that I use whenever I have it on my team. I particularly like using it on Gengar. A lot of things OHKO Butterfree, so that's why there's a focus sash. Because of this though, don't switch your Butterfree onto an opponent (unless your out of your sash or can predict your opponent not attacking). Use Tailwind so you're faster next turn. Sleep Powder will then hit cause of Compound Eyes, and then Dream Eat your way back to full health, which is also if I'm not mistaken a 2HKO (maybe 3) on Gengar. Bug Buzz is there for an extra attack in case you need it.
Note: You can swap out your Speed EVs for something else. Speed isn't needed in the Dream Eater setup because of Tailwind, but is nice to have if you instead want to come in and attack (semi) fast with Bug Buzz. I use Modest nature to increase it's SAtk even higher (as that also helps you recover HP faster w/Dream Eater), in trade for lowering it's unneeded attack.
Chibofree Modified
Butterfree @ Focus Sash
Calm/Compoundeyes
252Hp/252SpDef/4Def
-Tailwind
-Sleep Powder
-Supersonic
-Roost
Based off the Chibofree set with the Tailwind Sleep Powder setup, I instead use other moves for setups and stalling. I set up the EVs in this one to survive longer, especially against special attackers.
Wallfree
Butterfree @ Leftovers
Calm/Compoundeyes
252Hp/252SpDef/4Def
-Iron Defense
-Roost
-Bug Buzz
-Sleep Powder
I tried to turn Butterfree into a mixed wall with this set. Butterfree already has almost decent SDef, so I work into boosting Def similar to a strong Def Slowbro boosting it's SDef with Calm Mind. Butterfree can learn Iron Defense because of Metapod.
The set is mainly based around Iron Defense and Roost. You can then either use Bug Buzz and Sleep Powder for extra walling with Sleep status and Butterfree's strongest STAB attack, or perhaps switch it to Protect and Toxic, however in that case if you're up against a Steel or Poison pokemon, you can't do anything.
Extra Options
You can try out U-turn on Butterfree after setting up with a Tailwind, which won't do much because of Butterfree's low attack, but it still does some damage while switching out to someone who can take advantage of Tailwind's speed increase. This can be good to finish off a near dead opponent or destroy someone's use of Focus Sash. A lot of people will try to make Butterfree into a lead special attacker, but I feel it really isn't that effective with sub-par HP and Def, and Speed that isn't that impressive. I think it benefits more from it's status and helping moves.
EVs
EVs aren't that important on such weak pokemon. Especially since the first two sets rely heavily on focus sash, it's important to just focus on raising your special attack and speed. The only difference is the Wallfree, which puts EVs into special defense as your defense will be fine with Iron Defense.
Troublesome Pokemon
Watch out for weather effects like Hail or Sandstorm as they ruin my common Focus Sash setup. Also be careful of any pokemon with a quick strike move like Quick Atk or Extremespeed as they will finish you off before you can use Sleep Powder. Butterfree can barely compete in an OU environment as a lot of pokemon will have resistances or go be average against the Bug or Psychic move it may have. Additionally, Butterfree has low HP and Def, so watch out for any physical attacks (that are effective) and any Rock moves.
Written by ChiboSempai.