Chansey

Chansey is one the best specially defensive walls around thanks to its massive HP and Special Defense stats. Thanks to its bulk and access to Soft-Boiled to keep itself healthy, it is able to take on special attackers lacking physical moves such as Mega Alakazam, Starmie, Mega Charizard X, and Mega Charizard Y. Chansey also is an effective status inducer with either Toxic or Thunder Wave due to how effective it is at forcing switches and access to utility moves like Teleport, can be very useful to gain momentum for the team and bring its teammates in safely against any of it's checks. However, a terrible Defense stat makes Chansey unable to take any physical attacks well; Pokemon like Mega Beedrill, Melmetal, Mega Gyarados, and Snorlax can OHKO it with their attacks. Chansey also struggles with potential mixed attackers like Mega Charizard Y and Mega Venusaur for the same reason, being 2HKOed by their Earthquake. It even struggles against weak physical attacks from Zapdos and Mew, two Pokemon it is supposed to check, being heavily dented by their U-turn, and gets shut down by Calm Mind Mew, as Taunt turns it into setup fodder.