Head Smash and Brave Bird.
If it's enough to get it banned from STABmons, it's enough to get it banned from OU.
Giving Kartana access to every Grass and Steel move would get it banned as well, though with Spore and Shift Gear to work with alongside actually powerful STABs that shouldn't be a surprise.
>>32319420Not that anon, but giving Zygarde access to Xerneas and Yveltal's signature moves always seemed like a neat idea. It would also give Zygarde a viable Special set with Geomancy, Core Enforcer (remember that?), Earth Power, and Sludge Wave. This adds an element of unpredictability to Zygarde, limiting your sure-fire answers to Unaware Clefable. I'm looking at calcs, most of the other things in OU that would be able to stop it after a Geomancy would lose to regular Physical variants. Zygarde's base Special Attack isn't even 20 points lower than its base Physical Attack, after all.