Mothim

Honestly, Mothim is pretty generic as far as Bug / Flying types go. With pitiful defenses, good Special Attack, and mediocre Speed, like many of his Bug-type cousins, Mothim doesn't particularly stand out in any way. Furthermore, he isn't particularly good either due to his 4x weakness to Stealth Rock. Even with the gift of Quiver Dance this generation, Mothim still has issues differentiating himself from Butterfree and Masquerain, the former boasting higher Speed and Sleep Powder, while the latter has Baton Pass, Intimidate, and a wider movepool. Mothim is also much frailer than these two Bug-types, which makes setup opportunities harder to come by. Still, Mothim does have a few key traits which allow him to carve out a slight niche for himself. Mothim has Air Slash, while Butterfree does not, granting him a powerful secondary STAB move that has perfect neutral coverage with Tinted Lens and Bug Buzz. He also has the aforementioned Tinted Lens and a somewhat higher Speed stat to separate himself from Masquerain. On top of this, Mothim has a much higher Special Attack stat than his fellow Quiver Dancers, which allows him to hit harder immediately and easily obtain OHKOs and 2HKOs which the other two would struggle to get. In the end, though, the only reason you should be using Mothim is if you really want his power or wish to make a team around him; otherwise, it's usually more advantageous to just use Butterfree or Masquerain, as their access to Sleep Powder or Baton Pass generally make them much easier to fit onto a team.