Neutral nature, right? That could do the job. I recommend Naïve for a mixed attacker or Timid.
Greninja @ Life Orb
Ability: Protean
EVs: 4 Atk / 252 SpA / 252 Spe
Nature: Quirky / Naïve / Timid
-Gunk Shot / Ice Beam
-Hydro Pump
-Almost anything
-U-Turn / Almost anything