Meowstic (F) @ Choice Specs / Choice Scarf
Ability: Competitive
EVs: 4 Def or SpD / 252 SpA / 252 Spe
Timid / Modest Nature
- Psyshock / Psychic
- Signal Beam
- Thunderbolt / Energy Ball
- Dark Pulse / Hidden Power [Fire] / Hidden Power [Ice]
So, the Nature depends on how you want to run Meowstic. Quick sweeper, or Powerhouse.
The Choice item can also differentiate with the nature, or situation. The EV spread is in itself simple. That last point is just there to help survive against either a physical or special attack of some sort.
Running Specs with a Timid nature would give it some power, while running Scarf with Modest nature would give it a beneficial speed boost, while dishing out the pain. You can even switch it up to whereas running the Specs with Modest could give you the maximum amount of damage to dish out, while Scarf and Timid would almost Guarantee that you can outspeed pokes like Greninja, whom of which is a very big threat.
Psyshock should be the main choice here, since there are a lot of special walls in her Tier. You can run Psychic if you're really confident in her power, and also want a bit of extra STAB.
Signal Beam is a Necessity in this case. Without it, She would be defenseless against Dark adversaries. Also hits Grass Types pretty hard, and has a chance to confuse if the target hasn't been finished off.
Thunderbolt or Energy Ball really depend on what you want to cover. Both cover annoying Water Types, but T-Bolt can also eliminate any Flying Types that are a pain, while Energy Ball can help eliminate threats like Quagsire and Seismitoad.
The last move is pretty tricky. Dark Pulse is there to cover any Ghost Types you encounter. HP Fire is there to cover threats like Ferrothorn and Scizor. HP Ice is for Coverage against any Dragon Types.