Fun fact: one of the most feared Pokemon in Anything Goes is not Mega Rayquaza, or some Arceus forme… It’s Vivillon. Just thought you’d like to know.
Well “one of the most feared” is a bit of an exaggeration; she’s a bit niche and very high-risk/high-reward, but even that much is a hell of an achievement for a cookie-cutter early-game butterfly. Honestly I think this says less about Vivillon than about how heinously overpowered sleep is in Pokémon, even after being nerfed in four out of six generations, and how completely we all tend to forget about that most of the time. Smogon has a rule (and I think other communities use this as well) that you can only put one Pokémon to sleep at a time, and their influence on the competitive Pokémon community is so great that even in contexts where their rules don’t apply (like most official tournaments) people kind of act as if they did – partly, I think, because the strategies banned by rules like this are just incredibly dickish and make the game a lot less fun for everyone. Of course, in Smogon’s “anything goes” tier… well, anything goes. Vivillon is faster than Butterfree and gets Compoundeyes Hurricane, and Sun and Moon nerfed the cr@p out of Darkrai’s Dark Void, so if you want to spam a very high-accuracy sleep technique, she’s the one to do it with. I mean, yes, Quiver Dance is part of it, because without it Vivillon would be outrun and one-shot by practically everything, but when you have all the legendary Pokémon in the game to work with, the offensive presence of a Quiver Dance Vivillon, while significant, isn’t that big a deal – which is why we would never have this conversation in the “uber” tier, where the sleep rules still apply. Sleep really is just that good. This is one of the reasons you shouldn’t automatically defer to the competitive zeitgeist when choosing Pokémon and movesets for single-player, not even in end-game battle facilities – it’s not actually the same game.