Shadow Grumpig

Oh, you have an opportunity to nab a Shadow Spoink from a Rocket? If you're looking for PvE performance, then don't bother, it's trash.

Best PvE Offensive Moveset

• Psywave is slightly stronger than Extrasensory, and both are superior to Charge Beam.
• Psychic outperforms Mirror Coat on offense by a considerable amount. 
• Psywave is on the weak side for defense.
• Shadow Ball and Dynamic Punch lack STAB and are better for other Pokemon. 

Best PvE Defensive Moveset

• Extrasensory hits harder on defense, but is walled by Dark-type attackers.
• Charge Beam is inferior stat-wise, but is less likely to be resisted. 
• Shadow Ball is easy to dodge, but provides coverage against the weakness to Ghost-type attackers.
• Dynamic Punch is strong and provides counter-coverage against Dark Types.
• Psychic is better than Mirror Coat in every way, and is also the hardest to dodge. 

Psywave is a much better move than either Extrasensory or Charge Beam, easily making it the best option

Shadow Ball and Dynamic Punch combine to provide impeccable coverage at a moderate cost. Psychic and Mirror Coat are underwhelming