Domination!

Raichu VS Gyarados - Snap, crackle, pop on Gyarados.
Onix VS Mega Pidgeot - Bonk, clunk, and got dunked on.
Farfetch'd VS Machamp - Peck, peck, pecky.
Electabuzz VS Butterfree - Zap, zap, bye, bye, Butterfree.
Seadra VS Nidoking - Splashy splash, wash out!

WIN.

Adding Seadra to the party.

Team holding Gym:

Pokémon in the Gym: