This page shows the strategies to successfully beat Nidoking considering Nidoking's possible movesets. For details of Nidoking, such as evolution chart, CP and HP, refer the link above.
Super effective moves
Nidoking is weak to the types below. For list of moves by types, tap the name of types.
Strategy 1
Nidoking's moveset
The combination of Poison Jab and Earthquake is considered as the best moveset for Nidoking as an attacker and a defender.
When Nidoking use Poison Jab and Earthquake, Sandslash is one of the best options. It uses ground-type fast/charge moves which are very effective against Nidoking while cut damage of poison-type moves.
Best moveset
Mudshot and Earthquake are the best fast/charge moves for Sandslash to defeat Nidoking based on DPS, EPS, and type match-up.
When Nidoking use only bug-type moves or the combination of Fury Cutter and Earthquake, Fearow may work enough even though its CP is low. Bug- and ground-type moves are not very effective against Fearow while Fearow's Drill Run is ground-type which Nidoking is weak to. Since Spearow is easy to find, picking a Fearow with an optimal moveset is not difficult.
Best moveset
The combination of Peck and Drill Run is an optimal moveset for Fearow as an attacker based on DPS and EPS. Additionally, Drill Run is super effective against Nidoking.
A player may use water- or ice-type Pokemon if do not mind received damage. Those Pokemon's water- and ice-type moves are super effective against Nodking.
When Nidoking use only poison-type moves, Golem is the best. While reducing damage of poison-type moves, Golem's ground-type moves are super effective against Nidoking. Note that Golem is weak to Nidoking's Earthquake.
Best Moveset
The combination of Mud-Slap and Earthquake is the best moveset for Golem to beat Nidoking.
The game's update take Mud Shot away from Golem. Golem caught after August 20 do not have Mud Shot. Golem captured before the update still can use Mud Shot.