Serperior

Grass

Serperior's great Special Attack stat, Speed stat, and ability in Contrary allow it to be a powerful sweeper. Contrary boosts its Special Attack each time a Leaf Storm is used, allowing it to break past Pokemon like Toxapex, Mantine, and Porygon2, and its great Speed stat allows it to outpace most of the metagame including Pokemon like Mega Gallade, Landorus, and Mega Diancie. It also has great utility options with Glare, Substitute, and Leech Seed that allow it to wear down the opposing team. However, Serperior's mediocre bulk means that it is easily revenge killed by faster Pokemon like Mega Lopunny and Weavile, Choice Scarf users like Latios and Heracross, and priority users like Dragonite and Diggersby. Serperior also suffers from a lack of good coverage options, as it relies on Hidden Power Fire to hit Steel-types super effectively. It also has to rely on Leaf Storm to do major damage because of its mediocre Special Attack stat. Furthermore, it is hard to justify a spot on the team for Serperior when other Pokemon such as Celebi, Whimsicott, and Decidueye individually improve matchups significantly, such as Steel and Poison, Dragon and Dark, and Psychic, respectively.