Shadow Golurk

The Shadow Boost was honestly all that Golurk needed to really excel. This shadowy ghost is one of the better Ground Types in the game, and its Ghost sub-typing tends to help it a bit on that front.

Best PvE Offensive Moveset

• Mud Slap and Earth Power make Shadow Golurk a really good Ground Type attacker.
• Astonish and Shadow Punch are bad, but if you're desperate for a Ghost attacker then... go hunt some Gastly.
• Dynamic Punch is a great move, but not great on Shadow Golurk.

Best PvE Defensive Moveset

• Stick with Mud Slap. It beats out Astonish without breaking a sweat.
• All of Shadow Golurk's charged moves are great for defense. Dynamic Punch hits Dark types like Tyranitar hard but leaves it open to other Ghosts, Earth Power is objectively powerful but leaves Golurk a sitting duck against anything that resists Ground, and Shadow Punch has wide coverage and 3 bars, but fairly low power.

Mud Slap is more favorable for its significantly higher damage output. Astonish is all around a terrible fast move. 

Shadow Punch is a poor move too, but benefits from the low Energy cost and STAB. Earth Power also has STAB which makes it the most powerful move for Golurk, but Dynamic Punch might be more valuable for its wide coverage.