As for greninja, we dont have access to dark pulse etc but you can still assemble a nasty protean special attacker
being squishy and not even being able to take alot of chip dmg, you usually send him later in the fight to outspeed and clean things up with an attack boosting item like expert belt, or a life orb if you can steal one
and you can switch him into a psychic attack since it does no dmg. he gets stab + the bonus dmg from item and changes his resistances to suit the fight
I bred a decent one with hidden power fire and ivs in the 30s with one stat 25+
- surf/hydro pump (hits fire, ground, rock), resists fire, water, ice, steel
- hidden power fire (hits ice, bug, grass), resists fire, grass, ice, steel, fairy
- extrasensory (hits fighting and poison)
- bounce flying (lmao didn't have a good 4th move, so I kept this here) would prob replace with a dark pulse if I had it, shrugs to hit pyschic and ghost types