Spikes Greninja was my favorite too. However, I would use Gunk Shot as my coverage (for Tapus, Clef & Grass-type), plus dual STAB Dark Pulse + Water Shuriken/Hydro Pump.
It has perfect neutral coverage (your set get hard-walled by Slowbro & Starmie).
Greninja @ Life Orb
Ability: Battle Bond
EVs: 28 Atk / 228 SpA / 252 Spe
Naive Nature
- Water Shuriken / Hydro Pump
- Dark Pulse
- Gunk Shot
- Spikes / Extrasensory
28 Atk guarantee OHKO on Tapu Lele and Tapu Koko, high chance 2HKO max/max Bold Clefable and 2HKO AV Torn-T with a little prior damage. Dark Pulse + Water Shuriken as STAB. Last slot is either Spikes or Extrasensory.