Lucario

With impressive offensive stats coupled with a compelling ability in Adaptability and a splendid movepool, Mega Lucario is a hard-hitter in the 1v1 metagame. Mega Lucario's high Speed lets it outspeed and KO top-tier threats like Mega Charizard Y, Mega Pinsir, Mega Gardevoir, and Heatran, while its resistance to Normal-type attacks allows it to be a great counter to Porygon Z and Meloetta. In addition to this, its Steel typing provides a immunity to poison that gives it the upper hand against Mega Venusaur. Mega Lucario also is equipped with utility moves like Magnet Rise, which lets it defeat common Ground-type Pokemon like Golem, Donphan, and non-Choice Scarf Garchomp, and its pre-Mega evolution ability Inner Focus allows it to defeat Jirachi most of the time. Sadly, its typing also makes it weak to common offensive types including Fire and Fighting, which leaves it vulnerable to Pokemon like non-Choice Band Victini, Sawk, and Mega Charizard X, as well as the unique Thousand Arrows from Zygarde, which bypasses Magnet Rise. Mega Lucario also struggles to fit everything it wants on one set, leaving it vulnerable to common threats if it does not run the correct coverage move. Moreover, its subpar bulk doesn't help in taking other powerful attacks like Hydro Cannon from Greninja and Psycho Boost from Deoxys-S. Its physical sets get completely walled by Aegislash, while bulky Pokemon such as Primarina, Tapu Fini, and Dragonite are able to take hits from it and retaliate with their moves. Due to these factors, it faces tough competition from other Fighting- or Steel-type Pokemon like Magearna, Mega Metagross, Mega Lopunny, and Kommo-o.