Mawile

Mega Mawile is a force to be reckoned with in the 1v1 metagame, able to deal with top-tier threats such as Mega Gyarados, Porygon-Z, and Tapu Lele. Its ability, Huge Power, grants it the highest effective base Attack in the game, which it can boost even further with Swords Dance. A very solid typing in Steel / Fairy allows it to resist prevalent types like Normal, Psychic, Dark, and Fairy. Its natural bulk and pre-Mega ability Intimidate allow Mega Mawile to survive most neutral hits and even some super effective ones. However, Mega Mawile's abysmal Speed tier does it no favors, other than allowing it to almost always land Metal Burst successfully. There are also many common Fire- and Ground-types, such as Charizard, Heatran, and Donphan, which can handle Mega Mawile effectively.