Ability: Iron Fist
Item: Sitrus Berry
Moveset: Shadow Punch, Earthquake, Curse, Rock Polish
EVs: 252 Attack, 200 Speed, 58 HP
Basically have him safely in play to set up Rock Polish then pound away with his hard psychical attacks, Golurk should be able to take out one Pokemon, He always serves as a stall breaker by using a last resort curse to cause aftermath if he faints forcing the trainer to lose his pokemon or force a switch allowing you to set up your next pokemon. Golurk is good to counter a Ninjask as Curse carries on a baton pass.
You could use life orb over Sitrus Berry if you want more omp on your attack, or tweak down the speed for more bulk since you run rock polish.