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Huge powe
It's 88-104%, after a layer of spikes it dies, and even then we don't know if priority fairy type moves exist/what he has. You can switch garchomp in on him, but what if he predicts it and uses a fairy move?
You forgot to make it adamant.
Still, someone might want to try it out or something and then they can't use that mon. It doesn't seem fair to ban it, especially if it has other perks (they mentioned easier ev/iv stuff, maybe this raises ivs or gives increased ev gains)