Nihilego

Nihilego is capable of both attacking and tanking to a respectable extent. Its advantage lies in its Rock / Poison typing, which is good offensively against major forces in the 1v1 metagame in Fire- and Fairy-type Pokemon, like Mega Charizard X, Mega Charizard Y, Tapu Lele, and Tapu Fini. Nihilego's formidable special bulk allows it to tank strong moves like a Hydro Vortex from Tapu Fini with appropriate investment. Physically, its extremely frail Defense is just not enough to tank most super effective physical moves, especially from Steel- and Ground-type Pokemon like Mega Metagross, Mega Aggron, Zygarde, and Donphan. Pokemon who also carry Earthquake as a coverage move, like Dragonite, Haxorus, Sawk, and Mega Pinsir, will be able to easily knock out Nihilego. Lastly, its immediate power is usually not enough to shore up its awkward defense typing, leaving it wide open to Pokemon like Heatran, Zeraora, Mega Blaziken, and Necrozma, who can all outdamage Nihilego.