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 Valarie. If you want to see the attempt where he wins, skip ahead to 10:53
The basic strategy goes like this - Shedinja is an insane counter to this leader at the time of recording. It can take out 5/6 pokemon without any concern. The approach is best explained in the video, but as a side note a Parasect with Dry Skin is also ridiculously OP.
If you have any questions or want to try something other than this, just let me know! I'd love to help.
