Overview
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Like many of his peers, Nidoking inspires jealousy among others, and for good reason. Possessing a movepool fit for a king royalty (I don't like "king being repeated, but do w/e), Nidoking has access to a wide variety of attacks that give him exceptional coverage. This was not enough to satisfy his greed, though, as so last generation Nidoking was gifted him (it sounds like Nidoking is greedy for more because he got SF last gen as is) with the ability Sheer Force, ramping up his average attacking stats to formidable levels. The combination of those factors makes countering Nidoking extremely [MISSING WORD YO. Suggestions: laborious, arduous] before knowing his moves. Wearing down Nidoking down is also quite difficult, as he is immune to Life Orb recoil from Sheer Force-boosted moves, Sandstorm damage, and Toxic, and he resists Stealth Rock. The last three are a result of Nidoking's good typing, which lets him absorb Toxic Spikes and check common threats like Terrakion. Poison/Ground is also a great offensive typing, giving Nidoking excellent neutral coverage with just his STAB moves.
However, there are a number of factors that make it very hard for Nidoking to be effective in OU. That The same typing that gives him several offensive merits also results in common weaknesses to Ground, Water, and Ice-type attacks. A mediocre at best speed and unimpressive defenses make these Nidoking simple for offensive Pokemon to take advantage of. Finally, Nidoking faces stiff competition from Landorus-I, who is a faster, stronger, and bulkier as Sheer Force-abusing (check GP standards) Ground-type. Although these flaws may seem small in number in comparison to Nidoking's positive traits, overall(AC) they make Nidoking a tough sell in the OU metagame. Despite these flaws, though, Nidoking can be a fearsome wallbreaker if used effectively.
All-Out Attacker
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name: All-Out Attacker
move 1: Sludge Wave
move 2: Earth Power
move 3: Ice Beam
move 4: Flamethrower
item: Life Orb
ability: Sheer Force
nature: Modest(space)/(space)Timid
evs: 4 HP / 252 SpA / 252 Spe
Moves
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The best way to abuse Nidoking's excellent coverage is with an all-out attacking set. Nidoking's base 85 Special Attack stat is deceptively low, as but with Sheer Force(AC) it is effectively essentially becomes base 126. Sludge Wave is the strongest attack available to Nidoking, hitting most neutral targets extremely hard. Earth Power is a great complementary STAB move for him to use, hitting the Poison, Rock, and Steel-types that are resistant or immune to Sludge Wave. Between these two moves, Nidoking hits most pokemon at least neutrally. Because of this, the last two spots can be customized for the super effective coverage that you desire. Ice Beam hits the many Ground-types in OU for good damage, especially Ground/Flying types that resist his STAB moves. The preferred choice in the final slot is Flamethrower for hitting the multitude of Steel-types that are neutral, resistant or immune to Earth Power, like Skarmory, Scizor, Forretress, and Ferrothorn. Thunderbolt is also a good choice to hit bulky Water-types like Jellicent and Gyarados, getting giving Nidoking the famed BoltBeam coverage.
Although he can hit almost everything that he would want with the above moves, Nidoking's expansive movepool lets him run many situational moves. Nidoking has access to Superpower which allows him to 2HKO Blissey. Nidoking He also has access to Sucker Punch, which can surprise Psychic and Ghost-types like Latios, Latias, and Gengar trying to revenge kill. If your team has no other options for it, Nidoking can set up Stealth Rock, but if he has a free turn, Nidoking should have better things to do. Substitute is also helpful against offensive teams, easing prediction and letting Nidoking select the correct move for the threat in front of him without worrying about switches.
Set Details
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The preferred nature for Nidoking is Modest, since he will either outspeed most walls and or be outsped by most attackers regardless, but a Timid nature is useful for hitting before positive-natured base 80's like such as (Like should only be used for comparisons) Dragonite. Life Orb is by far the best item choice, giving a necessary boost to all of Nidoking's attacks. If using a physical move on the set(AC) like notably (same as above) Superpower or Sucker Punch, a Rash nature is best to preserve Nidoking's physical bulk for Rock and Fighting-type moves.
Usage Tips
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Nidoking is best used as a wallbreaker with strong attacks and good coverage(AC) making it that is extremely hard to switch into. He's also normally an early-game Pokemon that can weaken defensive cores. However, He lacks the bulk to be a pivot or the speed to clean up late game. He's also normally an early-game Pokemon that can weaken defensive cores. Whether or not Nidoking contributes defensively to the team depends on if the opponent has Pokemon on his or her opponent's team(AP) Against Pokemon that Nidoking he can check.(RP)(AC) For example, if they have a Terrakion or Clefable, Nidoking will be more important to keep healthy than against.
Team Options
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A Fighting-type like Lucario, Terrakion, or Conkeldurr is a good partner for Nidoking as it they can beat Blissey and Chansey, who can otherwise switch into Nidoking with impunity ("Impunity" is a big, cliched no-no. Think of something else if you can.) The real trouble with getting Nidoking to do damage (implied) is getting him in safely, so a slow U-turn or Volt Switch from Scizor or Rotom-W can work wonders. Like all offensive Pokemon, Nidoking appreciates having hazards down to punish the opponent's switches. Ferrothorn is a Stealth Rock or Spikes user that has good synergy with Nidoking, resisting Water and Psychic-type moves while being neutral to Ground and Ice-type attacks. In turn, Nidoking can check Fighting-types that threaten Ferrothorn. Sticky Web works very well in conjunction with Nidoking's great power and average speed to let him break Pokemon that would normally outspeed him like such as Garchomp.
Other Options
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Nidoking doesn't have many choices other than a straight special attacker to stay relevant. Although his Attack may seem more appealing, the higher base power of all of Nidoking's special moves makes a physically-based set inferior, along with the lack of a Sheer Force-boosted boost on Earthquake. A Choice Scarf set makes use of Nidoking's super effective coverage to be a good revenge killer. If used on a rain team, Surf and Thunder can find their way onto the set. Megahorn will destroy a Latios and or Latias switching in. Taunt and Super Fang can be used to help Nidoking get past walls, but he's usually better off attacking and greatly appreciates the coverage of 4 attacks.
Checks & Counters
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**Special Walls** Chansey counters Nidoking completely, not even (makes it sound like the attack drop is a good thing...) being 2HKO'd by Superpower with the attack drop factored in. Blissey also counters him completely except for Superpower. Gastrodon and Mega Venusaur are not weak to any of Nidoking's common moves and have the bulk to take neutral STAB ones while doing heavy damage back.
**Faster Attackers** Although they may struggle with getting in, most offensive Pokemon can check Nidoking. Latios and Latias will not be OHKO'd by Ice Beam and will do so in return with Psyshock. Alakazam can also revenge kill Nidoking. Garchomp must avoid Ice Beam(AC) but it can revenge kill with Earthquake and Ice Beam. Kyurem-B can take any move other than Superpower with ease while switching in and threaten to KO with Ice Beam.