Serperior

Serperior has cemented itself as a significant force to be reckoned with in the OU tier thanks to its ability Contrary's perfect synergy with Leaf Storm turning it into a huge snowballing threat, backed up by its high Speed stat and amazing utility options such as Glare, Taunt, Defog, Knock Off, and Leech Seed. With its Contrary-boosted Leaf Storm, Serperior acts as a fantastic cleaner for offensively oriented teams that can bulldoze past metagame staples such as Toxapex and Tapu Fini. It can also use Substitute to take advantage of switch-ins and either wear them down with Leech Seed or punish them with Glare. The combination of Taunt and Defog makes Serperior a great enabler for hyper offense teams, supporting teammates vulnerable to Stealth Rock, such as Dragonite, Mega Charizard X, and Volcarona. Its great Speed tier lets it get the jump on key Pokemon such as Kartana, Mega Latias, and Mega Medicham, and it also makes Serperior a great Choice Scarf user, able to outpace and revenge kill the likes of Ash-Greninja, Mega Swampert under the rain, and weakened targets like Mega Alakazam and Tapu Koko. However, Serperior is held back by its lack of coverage, and it has to rely on Hidden Power Fire to hit Pokemon like Mega Scizor, Ferrothorn, and Kartana. Serperior also struggles against common Pokemon like Magearna, Heatran, and Mega Charizard X, and it can't fit all of its utility options it wants in one set. Its Special Attack stat is also below average at best without relying on boosting with Leaf Storm, in which the low PP is exploited by a multitude of Grass-resistant Pokemon like Zapdos, Ferrothorn, and the aforementioned Magearna. Its Speed stat, while solid, leaves it outpaced by common Pokemon such as Tornadus-T, Greninja, and Tapu Koko. Finally, its typing leaves it vulnerable to U-turn and common attacking types such as Fire, Ice, and Flying.