Parasect KO'd five Pokemon.
And not just any 5 Pokemon, but Blastoise, Dragonite, Zapdos, Mew, and Articuno, in that order.
It's called "having a Substitute up before the next Pokemon comes into play."
That, and "Blastoise tastes delicious."
Oh, and the set I used was Spore, Substitute, Slash, Mega Drain
This doesn't happen very often, obviously, but damn, it was fun.
And if anyone was wondering about my opponent's 6th pokemon, it was a Charizard he started out with, who was able to score many critical hits in order to take down both Tentacruel AND Jynx. Lickitung took out the remains of Charizard, only to be thwarted by Blastoise.
Good Excel: The Bullet of Justice will always demolish evil! Remember that!
Excel: That's some dirty justice.
(Weird Anime Excel Saga)