Latias

Mega Latias is a metagame staple thanks to its bulk, movepool, and defensive profile. It can come in on common Pokemon like Heatran, Kartana, Rotom-W, Landorus-T, Zapdos, Rockium Z Garchomp, Mega Lopunny, and Battle Bond Greninja using Water-type moves consistently throughout a game. Mega Latias also outspeeds many of these Pokemon, notably Kartana, forcing them out with attacks like Ice Beam, Hidden Power, and Psychic. It's also one of the few Pokemon that can take any one move from Mega Medicham and threaten it back, giving faster-paced teams a decent answer to a Pokemon that usually requires a more passive switch-in. It's also the easiest answer to Swords Dance Gliscor to fit on teams. Mega Latias also has other options like Thunder Wave, Defog, and Calm Mind; its devastating Calm Mind set can outlast many offensive teams and threaten common balance and stall staples, including Toxapex, a common Haze user. However, Mega Latias struggles with four-moveslot syndrome. If its standard set drops Hidden Power Ground or Fighting, then Heatran, Excadrill, and Tyranitar can switch into it without much fear, while the same is true for Toxapex if it drops Psychic. It has some nasty weaknesses to Fairy, Ice, and Dark, being forced out by strong attackers like Tapu Lele and Mega Latios and Pursuit trapped by Tyranitar and Weavile. Mega Latias is vulnerable to poison and paralysis from Pokemon like Heatran, Toxapex, defensive Kommo-o, Zapdos, and Defog Gliscor, which can make it more difficult to check these Pokemon in the long run. It also struggles to break through threats like Magearna and Jirachi regardless of its set, and bulky foes like Clefable and Reuniclus sufficiently wall the utility set.