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The last pokemon that actually struck Prinplup gets the KOC for KOing Prinplup. If Scizor's Counter didn't end up doing damage to Prinplup before he fainted, then I think Rotom gets the KOC.
"Alright buddy, it is all up to you now. Do not screw this up!"
Sand Attack > Earthquake > Earthquake IF (Protective/Evasive Move) is issued successfully without transfer A1, THEN use Earthquake A1, pushing actions back.
Just noting that the ref prizes in this battle are incorrect. Eternal Drifter should get 1 UC, Leethoof should get 4 UC, and inanimate blob should get 10 UC.