Scyther

Scyther is one of the most threatening Pokemon in the GSC UnderUsed metagame. It is almost unmatched in terms of Speed, with the only notable Pokemon that outspeed it being Jumpluff, Crobat, and Electrode. It can pass Swords Dance or Agility boosts to its teammates before the opponent has a chance to properly react, and it also functions very effectively as a standalone sweeper thanks to its high Attack. Of the few viable Haze users and phazers available, an even lower number can take on a Swords Dance-boosted Scyther reliably. The only thing that prevents Scyther from being completely unstoppable is its limited attacking movepool—the strongest STAB attacks it can use are Hidden Power Flying and Hidden Power Bug, and using these means it can't use Hidden Power Ground.