Serperior

Serperior slithers across the battlefield as one of the most dangerous threats in the metagame thanks to its solid Speed stat, amazing ability in Contrary, decent typing, and wide range of utility moves, such as Glare, Taunt, Knock Off, Leech Seed, Reflect, and Light Screen. Its Speed allows it to get the jump on Pokemon like Keldeo, Latias, and Mega Metagross. With a Contrary-boosted Leaf Storm, Serperior serves as a fantastic cleaner and threatens key metagame staples like Excadrill, Clefable, Landorus-T, and Rotom-W. Contrary also allows Serperior to punish Defog, letting it take on Pokemon that it should have no business staying in against, such as Magma Storm Heatran. However, Serperior has no reliable coverage options outside of Hidden Power. Speaking of which, it has to choose between Hidden Power Fire or Hidden Power Rock, forcing it to pick between losing to Steel-types like Mega Scizor and Ferrothorn or Fire-types like Volcarona and Mega Charizard Y. Serperior also can't fit all of its utility options into one set. Its Special Attack stat is below average at best, forcing it to rely on boosting with Leaf Storm to threaten the opposing team, in which the low PP can be exploited by Pressure users like Zapdos. Additionally, Serperior is outpaced by Pokemon like Tornadus-T, Weavile, Mega Lopunny, and Mega Alakazam, and its typing leaves it vulnerable to U-turn and common attacking types like Ice, Fire, and Flying.