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Adamant is probably the best thing to do. You can always baton pass a speeds boost to it or give it some more speed EVs. Plus can't Mimikyu learn ominous wind? Plus can't you always use an X speed? I dunno, just throwing some ideas in the favor of adamant lol
Looking through the D ranks, I noticed that Mienshao was on the list. I don't know if Mienshao really deserves a D rank, since moves like Fake out, U-turn, Hi kick Jump... (Not to mention the occasional Regenerator ability). It's offensive stats are great, and not only that, but it has a...