Espeon

Thanks to its access to Growth, amazing Special Attack, and high Speed, Espeon can set up and either try to sweep or use Baton Pass to support another special attacker, which can turn manageable threats into devastating powerhouses in the blink of an eye. With a pure Psychic typing, Morning Sun, and STAB Psychic, it can switch into and threaten dangerous Pokemon such as Gengar, Machamp, Nidoking, and Tentacruel, which offensive teams sometimes struggle with.

However, Espeon is too fragile to take physical attacks from Snorlax, the most dominant Pokemon in GSC OU. In addition, status afflictions such as paralysis from Thunder Wave will compromise its potential. Furthermore, its movepool isn't ideal, which makes it hard to sweep without having the correct Hidden Power for Pokemon such as Tyranitar and Forretress.