See Full Series here: https://www.youtube.com/playlist?list=PLezAEu8shuO6qdBP5Qq_wjqRpDHhtOSDT

This is a Gym Leader episode where Metro describes exactly how he beats Revenant Keta.
If you want to see the attempt where he wins, skip ahead to 10:30

The basic strategy goes like this -
Psychic type 1 shots Primeape
Try to bait Dig on Hitmontop
Switch to Flying, finish.
Frogadier WITH PROTEAN Bounces on both Dark types (otherwise they one shot actual flying types).
Switches can actually benefit you here if you hit your bounces.
Use first psychic and flying to weaken Hawlucha when he comes out then finish with a third full-health Psychic type.
Use whatever's left for Sawk, he barely does anything but Endure.

Should be beatable with 4 pokemon as shown in the kill.

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