Metagross

Mega Metagross has access to great typing in Steel and Psychic, allowing it to effectively trade with many of the metagame's top threats, such as Serperior, Mega Alakazam, and Clefable. With its high Attack stat, access to Tough Claws, and great coverage options, Mega Metagross can be quite difficult to wall, especially before all four moves are revealed. Its Speed makes it faster than the majority of the non-boosted metagame, and with high stats in Defense and Special Defense, it can take one or two hits with no investment in its bulk. However, its low Speed pre-Mega can leave it vulnerable the turn it Mega Evolves. Although it has access to a ton of incredible coverage options, they can't all fit in one set, making it often walled by a lack of coverage rather than a lack of power. Finally, with much of its damage based in Tough Claws, it struggles against strategies that punish contact-based moves such as Static, Rough Skin, and Rocky Helmet.