Many people say the only Special Sweeper who can kill Blissey is a PorygonZ, who has Adaptive, Hyper Beam, and a Nasty Plot.
Well, let's see some others:
Alakazam: @ Choice Glasses
252 Evs Special Attack, 252 Evs Speed, 4 evs Special Defense
-Grass Rope
-Focus Blast
-Psychic
-Hidden Power [Ice]
Dealing a fairly nice type coverage, Zam seems to cover it's weaknesses well. With Focus Blast for Weavile/Tyranitar and any other Dark/Rock/Normal/Ice/Steel type, Zam deals quite an array of damage.
Grass Rope comes to stop Swampert
HP [Ice] is for maximum coverage.
Psychic is there for STAB, and fits there to handle possible AScarf Machamps, Infernapes, Brelooms, Blazikens, Weezings, Gengars, Heracrosses, and Toxicroaks.
*For the opportunity to not waste time, I will no longer include Evs/Natures as they can be interpreted by the readers.
Next up is Togekiss: Life Orb
Nasty Plot
Aura Sphere
Roost
Air Slash
With Nasty Plot, the ability to heal, and deal powerful damage Togekiss can definitely outstall blisseys, even those who Calm Mind with Ice Beam, as Togekiss can Roost and Defend itself with its 115 Base Special Defense. Roost not only heals, but grants nuetrality to Ice Beam, and since Togekiss goes first, it will not be weak to Ice Beam, and provided Aura Sphere has 2x Ice Beams PP, Blissey will certainly run out before Togekiss.
Nasty Plot out speeds Calm Mind, and Blissey will have a hard time Dealing with Kiss' Power.
Houndoom: @ Lum
-Beat-Up
-Nasty Plot
-Flamethrower
-Dark Pulse
He only needs Beat-up, and then once Blissey is finished, he can sweep away.
Lum is for Thunder Waves, otherwise if Blissey doesn't have thunder wave and uses ice Beam instead, Houndoom can switch in on the Ice Beam, and Beat-Up Blissey. Nasty Plot can also be used until Houndoom deals the final Beat-up Blow.
Gengar:
Focus Punch
Substitute
Thunder Bolt
Hidden power [Ice]
Classic Mc Gar. This works if Blissey uses Aromatherapy and Thunder Wave over Ice Beam and Calm Mind.
Celebi: Leftovers
Calm Mind
Leech Seed/Wish
Baton Pass/Psychic
Grass Rope
Heal off Ice Beams/Seismic Tosses with Leech Seed/Wish. Hit her hard back with your attack.
P.S. Does Future Sight go through Calm Mind?
Infernape: @ Life Orb
Nasty Plot
Flamethrower
Grass Rope
In-Fight
Mixed Sweeper.
Azelf: Chesto Berry
Nasty Plot
Rest
Psychic
Hidden Power [Fighting]
While Blissey tries to Seismic Toss you, just keep Nasty Plotting, then Rest off the damage and awaken with Chesto Berry. Make Azelf's Hp above 300, that way he can take 3 Seismic Tosses (using 3 Nasty Plots), and be at +6 Special Attack, then you can just Rest and Sweep.
HP [Fighting] is for Steels/Darks who resists your attacks.
*This 1 is creative, but not the best
Mismagius: @ Leftovers
Taunt
Shadow Ball
Calm mind
Pain Split/Thunder Bolt
Blissey cannot Seismic Toss you, Thunder Wave, Sing, or Calm Mind, which lets you build up your Calm Minds and heal off her Ice Beams with Pain Split, until she switches out.
Thunderbolt can also be used to for coverage over Pain Split.
Slowking: Leftovers
Slackoff
Nasty Plot/Calm Mind
Surf
Focus Blast
Resists Ice Beam, can outspeed Blissey's Calm Mind with Nasty Plot, can heal off damage. Focus Blast Owns Blissey.
Manaphy: Leftovers
Substitute
Ice Beam
Tail Glow
Surf
Ninetails:
Nasty Plot
Disable (Softboiled/Seismic Toss/Calm Mind)
Flamethrower
Energy Ball
With Disable, depending when you used it, Blissey cannot heal back it's life, or cannot harm you, or it cannot power up. All the while you are building up your Power. It would be good to Switch in on a Blissey who has just used Softboiled, use Disable, and then start Nasty Plotting.
Toxicroak: Expert Belt
Focus Blast
Nasty Plot
Shadow Ball
Vacuum Blade/Sludge Bomb
This way you can Sweep opponents, and with Expert Belt, your Vacuum Blade is now at a base power of 72.
Focus Blast gets Stab and Expert Belt and will deal 198x2= 396 Base Damage to Blissey, that is almost a BP of 400 Damage. Sure to reak havoc after just 1 Nasty Plot.
Shiftry:
Nasty Plot
Focus Blast
Explosion/Leaf Storm
Dark Pulse
Focus Blast+Dark Pulse for coverage, and own anything with Leaf Storm/Explosion.
Just FOR FUN TO PISS OFF BLISSEYS, nothing for real:
Smeargle: @ ANYTHING
Imprision
Seismic Toss
Ice Beam
Mean Look
Well, let's see some others:
Alakazam: @ Choice Glasses
252 Evs Special Attack, 252 Evs Speed, 4 evs Special Defense
-Grass Rope
-Focus Blast
-Psychic
-Hidden Power [Ice]
Dealing a fairly nice type coverage, Zam seems to cover it's weaknesses well. With Focus Blast for Weavile/Tyranitar and any other Dark/Rock/Normal/Ice/Steel type, Zam deals quite an array of damage.
Grass Rope comes to stop Swampert
HP [Ice] is for maximum coverage.
Psychic is there for STAB, and fits there to handle possible AScarf Machamps, Infernapes, Brelooms, Blazikens, Weezings, Gengars, Heracrosses, and Toxicroaks.
*For the opportunity to not waste time, I will no longer include Evs/Natures as they can be interpreted by the readers.
Next up is Togekiss: Life Orb
Nasty Plot
Aura Sphere
Roost
Air Slash
With Nasty Plot, the ability to heal, and deal powerful damage Togekiss can definitely outstall blisseys, even those who Calm Mind with Ice Beam, as Togekiss can Roost and Defend itself with its 115 Base Special Defense. Roost not only heals, but grants nuetrality to Ice Beam, and since Togekiss goes first, it will not be weak to Ice Beam, and provided Aura Sphere has 2x Ice Beams PP, Blissey will certainly run out before Togekiss.
Nasty Plot out speeds Calm Mind, and Blissey will have a hard time Dealing with Kiss' Power.
Houndoom: @ Lum
-Beat-Up
-Nasty Plot
-Flamethrower
-Dark Pulse
He only needs Beat-up, and then once Blissey is finished, he can sweep away.
Lum is for Thunder Waves, otherwise if Blissey doesn't have thunder wave and uses ice Beam instead, Houndoom can switch in on the Ice Beam, and Beat-Up Blissey. Nasty Plot can also be used until Houndoom deals the final Beat-up Blow.
Gengar:
Focus Punch
Substitute
Thunder Bolt
Hidden power [Ice]
Classic Mc Gar. This works if Blissey uses Aromatherapy and Thunder Wave over Ice Beam and Calm Mind.
Celebi: Leftovers
Calm Mind
Leech Seed/Wish
Baton Pass/Psychic
Grass Rope
Heal off Ice Beams/Seismic Tosses with Leech Seed/Wish. Hit her hard back with your attack.
P.S. Does Future Sight go through Calm Mind?
Infernape: @ Life Orb
Nasty Plot
Flamethrower
Grass Rope
In-Fight
Mixed Sweeper.
Azelf: Chesto Berry
Nasty Plot
Rest
Psychic
Hidden Power [Fighting]
While Blissey tries to Seismic Toss you, just keep Nasty Plotting, then Rest off the damage and awaken with Chesto Berry. Make Azelf's Hp above 300, that way he can take 3 Seismic Tosses (using 3 Nasty Plots), and be at +6 Special Attack, then you can just Rest and Sweep.
HP [Fighting] is for Steels/Darks who resists your attacks.
*This 1 is creative, but not the best
Mismagius: @ Leftovers
Taunt
Shadow Ball
Calm mind
Pain Split/Thunder Bolt
Blissey cannot Seismic Toss you, Thunder Wave, Sing, or Calm Mind, which lets you build up your Calm Minds and heal off her Ice Beams with Pain Split, until she switches out.
Thunderbolt can also be used to for coverage over Pain Split.
Slowking: Leftovers
Slackoff
Nasty Plot/Calm Mind
Surf
Focus Blast
Resists Ice Beam, can outspeed Blissey's Calm Mind with Nasty Plot, can heal off damage. Focus Blast Owns Blissey.
Manaphy: Leftovers
Substitute
Ice Beam
Tail Glow
Surf
Ninetails:
Nasty Plot
Disable (Softboiled/Seismic Toss/Calm Mind)
Flamethrower
Energy Ball
With Disable, depending when you used it, Blissey cannot heal back it's life, or cannot harm you, or it cannot power up. All the while you are building up your Power. It would be good to Switch in on a Blissey who has just used Softboiled, use Disable, and then start Nasty Plotting.
Toxicroak: Expert Belt
Focus Blast
Nasty Plot
Shadow Ball
Vacuum Blade/Sludge Bomb
This way you can Sweep opponents, and with Expert Belt, your Vacuum Blade is now at a base power of 72.
Focus Blast gets Stab and Expert Belt and will deal 198x2= 396 Base Damage to Blissey, that is almost a BP of 400 Damage. Sure to reak havoc after just 1 Nasty Plot.
Shiftry:
Nasty Plot
Focus Blast
Explosion/Leaf Storm
Dark Pulse
Focus Blast+Dark Pulse for coverage, and own anything with Leaf Storm/Explosion.
Just FOR FUN TO PISS OFF BLISSEYS, nothing for real:
Smeargle: @ ANYTHING
Imprision
Seismic Toss
Ice Beam
Mean Look