Blastoise

Mega Blastoise's ability to counter some of 1v1's most prominent threats such as Dragonite, Mega Charizard Y, and non-Thunder Punch Mega Metagross makes it a great anti-metagame Pokemon. Mega Launcher is a fantastic ability, since it boosts Mega Blastoise's Aura Sphere and Dragon Pulse by 50%, allowing Mega Blastoise to break through a myriad of threats such as Mega Lopunny and Mega Charizard X. However, Mega Blastoise's mediocre stats force it to focus solely on a particular stat to gain KOs, and this is an issue, as it needs lots of bulk to survive hits but also needs to run a lot of Special Attack and Speed investment along with a Speed-lowering move to defeat foes. Additionally, Mega Blastoise is weak to several Electric- and Grass-types and Pokemon with coverage of either type such as Zeraora, Serperior, Thunder Punch Mega Metagross, and Grass Knot Greninja. Finally, it faces a lot of competition from other, much more viable Water-types such as Mega Gyarados, Greninja, and Tapu Fini.