Jesus, that was rough.
I beat it with:
Ivysaur - Razor Leaf
Beedrill - String Shot
Ekans - Leer
Mankey - Fury Swipes
Ratticate - Sucker Punch
Butterfree - Confusion
I kept Ekans in the center to lower the Defense of everything. Then I moved Ivysaur and Butterfree to the same side as the Geodude each time and moved Mankey and Ratticate to the side with the big wave.
I tried Pikachu with Thunder Wave for a long while, but it just didn't work. I also tried Pikachu's Growl too, but that just made everything avalanche worse. But when I caught Ekans I figured that he could lower Geodude's Defense to manageable levels.
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Xbox GT: PrivateBiscuit1
Down with Zhang. Let there be Biscuit!