Gengar is easily the hardest mon to switch into rn. Clef doesn't have to hit its thunders, the move is there to scare out pex. Spdef rachi allows you to ude full phys def corvi, which can tank conk. Scarf hydra is the premier offense check. Gastro is the mandatory ground and water inmunity, e-belt zeraora doesn't 2hko with grass knot.
https://pokepast.es/bfeec88d49be71f4
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https://pokepast.es/1086d5428823574d