Blissey

Blissey is incredibly specially bulky and has no special weaknesses, making it a fantastic general purpose special wall. Its options for team support are also superb, as it possesses one of the most valuable support moves in the tier, Heal Bell, plus moves such as Wish and Toxic. Blissey's physical bulk is surprisingly acceptable, but it still leaves it weak to the strong physical attackers in the tier, such as Deoxys-A and Groudon.

Unfortunately, its offensive presence is minimal, forcing it to rely on Toxic and Seismic Toss to pressure foes, which can't significantly threaten foes such as Snorlax and Metagross. This passivity has also given rise to specialist sets from special attackers that can beat it one-on-one by taking advantage of its reliance on Toxic to set up, such as Substitute + Calm Mind Mewtwo and Rest + Calm Mind Kyogre. Furthermore, it has a significant Spikes weakness and lets its users in easily. Finally, it faces competition as a check to Latios and Latias from Snorlax, which has much more offensive presence but somewhat less bulk and longevity.

Blissey generally fits best on defensive or balance teams that can provide the significant support it needs and take advantage of the equally significant support it provides.