Pretty sure that topic's over, but whatevs. Greninja was banned in OU because it put teambuilding into such a huge strain. There was no reason to not use it. Fairy-types once were the one of the many things that could stop it but it got Gunk Shot in ORAS. STAB Hydro Pump coming from 103 SpA + Protean + Life Orb was bonkers.
It was versatile as all hell, too (seriously wtf is its movepool). Offensive Spikes worked, Life Orb worked, etc. but for the most part Life Orb was the most common Greninja. Physical sets were lame. No one ran physical Greninja.
Sure it was frail af, but when you have such a 'threat' in your tier, it makes sense to ban it. Your meta fails to improve otherwise.
THEN AGAIN