All you need is 6 pokemon around level 90 or higher. You need at least:

2 ghost pokemon (preferably Haunter or Gengar)  Shadow ball.

1 poison pokemon (Nidoqueen Nidoking) helping head, fighting attacks and poison sting.

1 psychic pokemon (Alakazam ) psychic.

1 Flying pokemon (Pidgeotto) whirl wind.

1 grass type pokemon (Venausaur) Leech seed.

First to slots belong to the ghost types, then after the grass type pokemon, then the poison type pokemon and at the end, put pidgeotto at the end. don't let him get hit by any pokemon. Use potions when necessary. Charizard with earthquake will also help.

003MS Venusaur

Bulldoze/Earthquake Roar
Synthesis Sunny Day
042MSGolbat (1 to 5)
Acrobatics Whirlwind
Rest ---


Psychic Reflect Type Psychic/Bulldoze Reflect Type
Light Screen Recover Light Screen Rest
082MSMagneton (Recommended)
Discharge Charge Beam
Light Screen Rest
Psychic Quiver Dance
Rest Whirlwind