Blissey returns for yet another round in the Uber tier as the premier special wall. No Pokemon does Blissey's job better, with the possible exception of her sister Chansey. Few special attackers can break through Blissey thanks to her titanic Special Defense and HP stats. Almost any team, particularly stall teams, will appreciate Blissey's ability to sponge assaults. While Chansey gives stiff competition with better bulk, Blissey's consistent passive recovery allows her to switch in and out of battle without using Wish or Softboiled as often. Thanks to Leftovers recovery, Blissey can take weaker hits such as Dialga's Dragon Pulse better than Chansey can. As a bonus, Blissey can even surprise opponents with her underwhelming but workable Special Attack.
Blissey is the only Pokemon in Ubers other than Chansey who can wall such a wide variety of special threats such as Palkia, most variants of Dialga and Kyogre, non-Specs Reshiram, most Calm Mind Arceus, and Lugia. Seismic Toss is generally the most reliable attacking move, as it dents bulky Pokemon and offensive Calm Mind Kyogre, who will otherwise laugh at Blissey's pathetic attacks. Ice Beam is still a viable move, as some common Blissey switch-ins, such as Groudon, Zekrom, Garchomp, and Rayquaza, hate it. Toxic complements this set well, as the combination of Protect and Wish can very easily stall Pokemon to death. Toxic can also be used to cripple several threats, such as Kyogre, Darkrai, and Giratina-O, on the switch-in. Snatch can be used to steal support moves from the likes of Arceus, and allows Blissey to beat Calm Mind Dark Arceus, a deadly threat to stall, by poisoning it with Toxic and then preventing Arceus from using Refresh with Snatch. Heal Bell can be used over Protect if your team needs a Wish passer as well as a cleric. Heal Bell also saves Blissey from opposing Toxic Spikes.Team Options & Additional Comments >>>
Blissey's movepool is extremely extensive, and while its most effective moveset is the one listed above, there are a couple moves that have niche uses in Ubers. Calm Mind lets her beat Giratina-O, Manaphy, and Kyogre in a Calm Mind war, but requires Blissey to use special attacks and sacrifices much of her utility. Light Screen seems odd on Blissey, but prevents Choice Specs Kyogre from 2HKOing with Water Spout. Sing can put an opponent's Blissey counter to sleep, but its shaky accuracy makes it less than desirable. Rest is usually inferior to Wish and Softboiled, but can prove useful against opposing Blissey or teams with Toxic Spikes. Block can be used alongside Toxic to trap and eliminate Wobbuffet. Copycat may seem like a strange option on Blissey, but it can be useful against opponents such as Forretress, as it allows Blissey to potentially copy Spikes, Toxic Spikes, or even Rapid Spin. Gravity also has some niche use in Ubers, as many Pokemon in Ubers rely on moves with unreliable accuracy, especially Darkrai with its 80% accurate Dark Void and 70% accurate Focus Blast. It can also allow Garchomp and Groudon to abuse their powerful STAB Earthquakes more effectively.
Blissey also has a couple options to make herself a little more threatening to opposing teams. With sun support from Groudon, Blissey can use Flamethrower to ward off Steel-types looking to abuse their immunity to Toxic. Flamethrower in the sun OHKOes Forretress, Ferrothorn, and most Scizor, nearly OHKOes Lucario, and 2HKOes Metagross factoring in Stealth Rock. Grass Knot hits Groudon, a common switch-in to Blissey, and also hits many other Ubers with 120 Base Power. Finally, Counter can be used to catch physical attackers off-guard. Blissey has a surprisingly large amount of physical bulk, and if she Counters a weak physical attack from foes such as Palkia, Dialga, defensive Groudon, Choice Scarf Garchomp, or even Scizor wthout Superpower, it's sure to take them out.
Checks and Counters
Bulk Up Dialga is arguably the best Blissey counter. Dialga is immune to Toxic, and can easily set up on Blissey. Powerful physical attackers, such as Groudon, Zekrom, Rayquaza, and Garchomp, can make Blissey's life hard. However, Ice Beam will do massive damage to Garchomp and Rayquaza, and none of them like being hit by Toxic. Ho-Oh can easily come in on anything barring Toxic, and set up 101 HP Substitutes for blocking Blissey's Toxic and taking Seismic Toss twice. From there, Sacred Fire or Brave Bird can easily end Blissey's life. However, take note that Brave Bird recoil will be massive when hitting Blissey due to her enormous HP.
Mixed Dialga, Palkia, and Giratina-O can surprise Blissey with physical attacks. Dialga in particular can be a problem, as it is immune to Toxic. Giratina-O can avoid Toxic with Substitute, and set up on Blissey with Calm Mind. Outrage from mixed Giratina-O can easily 2HKO Blissey. Mewtwo can easily OHKO Blissey with a boosted Psystrike. If Darkrai can get a Nasty Plot boost, it will 2HKO Blissey with Focus Blast.
Kyogre and Giratina can use a combination of Sleep Talk, Rest, and Calm Mind to easily set up on Blissey. In the rain, Manaphy can easily set up Tail Glow on non-Calm Mind Blissey and 2HKO it with a +3 Surf. Choice Specs Kyogre and Reshiram also have the ability to 2HKO Blissey with Water Spout or Blue Flare (which requires sun support). Steel and Poison Arceus can set up on Blissey easily due to their immunity to Toxic and access to recovery moves. Any Arceus set with Refresh can easily use Blissey as setup bait. Ground Arceus and Extreme Killer Arceus can OHKO Blissey with a +2 Earthquake or ExtremeSpeed.
Wobbuffet can switch into Blissey and use Tickle several times to lower her Defense. After this, Blissey will be KOed by Pursuit from Scizor or Tyranitar. Wobbuffet can also use Encore on Blissey and switch in a sweeper such as Mewtwo or Giratina-O to take advantage of the free setup time. Ferrothorn has Leech Seed, which allows it to easily out-heal Seismic Toss from Blissey, and Iron Barbs, which damages Blissey every time it uses Seismic Toss on Ferrothorn. Meanwhile, Ferrothorn is free to either set up Spikes or hit it hard with Power Whip. Skarmory can also set up Spikes on it for free, and it also has Roost to shrug off repeated Seismic Tosses.