Get 6 low-level Rattata
Teach them Endeavor and Quick Attack
Put Focus Sashes on all of them.
Use Endeavor on the first turn (opposing 'mon will take down to 1 because of Focus Sash and they be taken down to 1 too)
Use Quick Attack.
Repeat until you have utterly destroyed the opposing team
Note: Ghost type 'mon are your enemy with this team