My Nido runs Nidoking @ Life Orb Trait: Sheer Force Modest Nature, 252 SpAtt, 252 Speed Earth Power Sludge Wave ?? ?? I was thinking Flamethrower/ Ice Beam /Thunderbolt. This is a Special Sweeper, so please don't put mixed move sets and Stalling or Health Recovery moves. I checked the moveset page
Nidoking (M) @ Life Orb Ability: Sheer Force EVs: 252 SpA / 4 SpD / 252 Spe Modest Nature IVs: 0 Atk - Earth Power - Sludge Wave - Ice Beam - Thunderbolt / Superpower Ice Beam and Thunderbolt are good options because they are boosted by Sheer Force, have good BP, and have vast and relevant coverage. However, you can consider Superpower over Thunderbolt to hit Special Defense walls like Blissey or Umbreon that may be inclined to switch into Nidoking's attacks. Remember to use those last 4 EVs. I recommend putting them into Special Defense to help you switch into Fairy moves (which are primarily Special).