Nidoking

Thanks to its excellent offensive typing, ability in Sheer Force, powerful STAB moves like Sludge Wave and Earth Power, and excellent coverage moves like Fire Blast, Ice Beam, and Thunderbolt, Nidoking is a very powerful wallbreaker. It can hit a large portion of the tier for super effective damage, pressuring plenty of Pokemon like Skarmory, Primarina, and Amoonguss. Even though Nidoking is one of the most dangerous threats in the tier, its mediocre Speed tier and bulk mean it can't find many opportunities to wallbreak, mandating pivot support to get it onto the field safely. Nidoking also relies on its Life Orb to do massive damage, so it despises Knock Off from the likes of Nihilego and Thundurus-T. Its typing also doesn't benefit it much defensively, leaving it weak to common attacking types like Ground, Water, and Psychic from Pokemon like Excadrill, Azumarill, and Azelf. Furthermore, despite being a Ground-type, Nidoking doesn't provide a functional Electric immunity for its team, being outsped by Rotom-W, Rotom-H, and Thundurus-T and getting hit hard by their other moves. This lack of defensive utility makes it hard to justify over other Pokemon that share its Ground or Poison typing like Hippowdon, Excadrill, and Nihilego. Nidoqueen, while weaker, has more bulk than Nidoking, allowing it to fit Stealth Rock for role compression, and its lower Speed isn't a hinderance in UU.