Timid/Modest
252 Special Attack 252 Speed 6 Hp
~ Seed Flare
~ Air Slash
~ Earth Power
~ Hidden Power Ice
6 HP / 252 SpA / 252 Spe
Using a Choice Scarf on such a fast Pokémon may seem strange, but Shaymin-S can be both a great revenge killer and a decent lead with it.
One of the most important decisions to make when using Choice Scarf Shaymin-S is what nature it will use, as the nature affects both the moveset and the Pokémon Shaymin-S is able to effectively revenge kill. When using Shaymin-S as a revenge killer, Modest is generally the best nature to use. With Choice Scarf and a Modest nature, Shaymin-S reaches a Speed stat of 529, meaning that the only somewhat common Pokémon in Ubers who will outspeed Shaymin-S are Timid Choice Scarf Darkrai, Timid Choice Scarf Shaymin-S, and Choice Scarf Mewtwo. Thanks to the power boost from its Modest nature, Shaymin-S's Seed Flare will OHKO a 4 HP / 0 SpD Kyogre 100% of the time, after it switches into Stealth Rock. Modest also makes Leaf Storm a viable option for Shaymin-S, as the extra base power allows Shaymin-S to OHKO both a max HP Kyogre and a 4 HP / 0 SpD Darkrai, after Stealth Rock damage. However, be warned that after getting a kill with Leaf Storm, Shaymin-S can be easily set up on by Calm Mind users, such as Latias and Mewtwo, due to the Special Attack drop. Leaf Storm also lacks the 80% chance (68% chance when taking accuracy into account) of halving the opponent's Special Defense that Seed Flare has. Generally, Seed Flare should always be the Grass-type move of choice, unless your team needs the KOs that Leaf Storm can provide. Timid is a workable nature, but it unfortunately loses the 100% chance to KO a 4 HP Kyogre, after Stealth Rock, with Seed Flare. Don’t bother using Leaf Storm on a Timid Shaymin-S, as the only important OHKO gained is on 4 HP / 0 SpD Kyogre after Stealth Rock. When using Choice Scarf Shaymin-S as a lead, Timid is the best nature, as it allows Shaymin-S to outspeed Choice Scarf Darkrai leads. No matter which Grass-type move or nature you choose, one of the biggest selling points of Choice Scarf Shaymin-S is its ability to destroy Rock Polish Groudon. After one Rock Polish, most Groudon will reach a Speed stat of 500, which is still outsped by Choice Scarf Shaymin-S. Shaymin-S can switch into Groudon’s Earthquakes as well, and OHKO it with Seed Flare. Because of these factors, Choice Scarf Shaymin-S is one of the best offensive answers to Rock Polish Groudon.
In addition, to provide a secondary STAB attack, Air Slash has a 60% flinch rate (57% when taking accuracy into account), thanks to Serene Grace. This can get Shaymin-S out of tough situations. For example, if Shaymin-S is up against a Choice Scarf Palkia with 79% of its health left. Seed Flare will not OHKO it, but Air Slash can 2HKO Palkia when it is at this health; thus, Palkia will be either forced to switch out or die if Air Slash flinches it. Air Slash also hits a majority of the Uber metagame for neutral damage, the only significant Pokémon who resist it are Dialga, Metagross, and Tyranitar. The main purpose of Earth Power is to slam Dialga and Metagross switch-ins, with most Metagross being 2HKOed, while most offensive Dialga are 2HKOed (be warned, though, specially defensive Dialga will live through two Earth Powers, and will still often live even after a Special Defense drop). Finally, Hidden Power Ice allows Shaymin-S to revenge kill Garchomp, opposing Shaymin-S, and Dragon Dance Rayquaza (as long as it lacks ExtremeSpeed).
Generally, Choice Scarf Shaymin-S’s biggest problems are Pokémon with resistances to Grass-type moves that switch in to take advantage of Shaymin-S. The most problematic of these is Choice Band Scizor. If Choice Band Scizor has max Attack, it will do at least 53% to Shaymin-S with Pursuit as it flees. This means that if Shaymin-S takes damage from Stealth Rock when it switched in, and Pursuit as it switches out, Shaymin-S will be KOed by Stealth Rock the next time it switches in. Other Scizor variants can still do a heavy amount of damage to Shaymin-S with Bullet Punch and U-turn. Enemy Shaymin-S can also take advantage of Seed Flare and Earth Power, and proceed to OHKO your Shaymin-S with Air Slash as long as it has taken Stealth Rock damage. Dialga’s 4x resistance to Seed Flare and a resistance to Air Slash gives it a relatively easy time switching into Shaymin-S, and can use the free turn to set up Bulk Ups, Stealth Rock, or outright KO Shaymin-S with Draco Meteor, Fire Blast, or Outrage (if it’s a Choice Band user). Rayquaza can take a Seed Flare, thanks to its 4x resistance to Grass-type moves, and can switch into Earth Power as well thanks to its immunity. Rayquaza can use the time to set up a sweep with Swords Dance (or Dragon Dance, as long as it has ExtremeSpeed), or OHKO Shaymin-S with Draco Meteor if it's mixed. Lugia can switch into Seed Flare and Earth Power as well, and will always OHKO Shaymin-S with Ice Beam after Stealth Rock damage. Giratina’s massive defensive stats and resistances allow it to take Shaymin-S’s attacks with ease, and waste Shaymin-S’s PP with Rest and Pressure, as long as Seed Flare does not get too many Special Defense drops. Latias can take any of Shaymin-S’s attacks, and can use the time to set up Calm Minds or have a 92% chance of OHKOing Shaymin-S with Dragon Pulse after Stealth Rock damage. Blissey has no problems with any of Choice Scarf Shaymin-S’s assaults either, and will either cripple Shaymin-S with Toxic or Thunder Wave, or OHKO Shaymin-S with Ice Beam after it has taken damage from Stealth Rock. A specially defensive Skarmory can easily switch into most of Shaymin-S’s moves as well, and Whirlwind it away, forcing Shaymin-S to take more damage from Stealth Rock if it is in play. If Skarmory has Brave Bird, it can OHKO Shaymin-S, if it has taken damage from Stealth Rock beforehand. Finally, although Wobbuffet cannot switch into Seed Flare, nor does it like Air Slash’s flinch rates, Wobbuffet can easily revenge kill Choice Scarf Shaymin-S, due to Shadow Tag and Mirror Coat.
Because of these problems, a mixed Dialga can be a good teammate for Choice Scarf Shaymin-S. Mixed Dialga can lure in Blissey, and do severe damage with Outrage or Brick Break. Latias may think it's safe after Dialga uses Draco Meteor, only to be OHKOed by Outrage. Dialga can also roast Skarmory with Fire Blast if it dares to switch in. If running Hasty with max Speed, mixed Dialga can destroy Adamant Swords Dance Rayquaza, and pose as a Choice Scarf user to defeat Wobbuffet. Dialga can also switch into Air Slashes from opposing Choice Scarf Shaymin-S, and scare them off with the prospect of OHKOing it. Gengar can lure in Scizor, only to OHKO it with Hidden Power Fire, as long as it is not raining. Life Orb Gengar can also OHKO Rayquaza with Icy Wind, assuming Stealth Rock is in play, for Shaymin-S if Rayquaza attempts to set up a Swords Dance. If Dragon Dance Rayquaza is an issue, Gengar can also be equipped with a Choice Scarf to destroy it with Hidden Power Ice, though this Gengar is especially vulnerable to Scizor. The Tickle Wobbuffet plus Pursuit strategy (usually used with either Tyranitar or Scizor) can remove both Lugia and Blissey from the battlefield for Shaymin-S. Both Scizor and Tyranitar are also capable of switching into Latias’s Dragon Pulse, and can either Pursuit her as she flees, or OHKO her with their super effective STAB attacks. Groudon can take care of Bulk Up Dialga in case it attempts to set up on Shaymin-S, as long as Dialga has not used Bulk Up too much. Groudon can carry Overheat to lure and OHKO Skarmory as well. Groudon’s huge base 150 Attack stat will scare away Blissey, and will allow Groudon to do a massive amount of damage to Scizor with Earthquake or Fire Punch. A Blissey of your own can defeat any Dialga who lack physical attacks, any Shaymin-S who lack Leech Seed, Latias who lack Refresh or Safeguard, and Lugia. Mixed Dialga can be very difficult to handle if it switches into any of Shaymin-S’s attacks with the exception of Earth Power; thus, it's best to revenge kill it with Pokémon that have STAB super effective attacks, such as Groudon, Choice Band Garchomp, and Lucario. Darkrai can be used to set up on Lugia and Giratina, and then crush them with Nasty Plot-boosted Dark Pulses. Darkrai can also destroy a weakened Latias, though Darkrai cannot safely switch in to Latias’s Dragon Pulse. Mewtwo can work well as a teammate, particularly an all-out attacker with Life Orb. Mewtwo can lure Scizor in, only to OHKO it with Fire Blast. Mewtwo can also run Selfdestruct to get a surprise KO on Blissey. If using Taunt and Calm Mind, Mewtwo can easily set up on Lugia and Giratina. Finally, Mewtwo can easily revenge kill opposing Shaymin-S with Ice Beam, if they lack Choice Scarf.
Choice Scarf Shaymin-S can be an acceptable lead as well. Thanks to Choice Scarf, Shaymin-S is able to outspeed Deoxys-S, and 2HKO it with Air Slash. At the worst, Deoxys-S will only be able to set up one entry hazard (assuming Air Slash does not miss), and at best Deoxys-S will be unable to get any entry hazards up against Shaymin-S, due to a flinch from Air Slash! Another common lead, Groudon, must make a heavy investment in Special Defense EVs and carry a Special Defense-boosting nature to survive Seed Flare reliably. Something to note about lead Choice Scarf Shaymin-S is that it often relies on Air Slash’s flinch rate to beat other leads. For example, Shaymin-S must flinch Deoxys-A, or else Deoxys-A will OHKO Shaymin-S with Ice Beam. In a more extreme example, Timid Shaymin-S only has a 28% chance of 2HKOing Darkrai with Air Slash, and thus must often flinch Darkrai twice in order to beat it. It is often best to take the chance with Deoxys-A, as its power makes it hard to switch into. Darkrai, on the other hand, can be dealt with by a Sleep Talk Kyogre. When using lead Choice Scarf Shaymin-S, Hidden Power Fire is a viable option, as it will not only destroy Scizor leads, but it will also OHKO any Forretress or Skarmory switch-ins as well. The main problem with Hidden Power Fire is that it requires Shaymin-S to lower its Speed IV to 30, meaning that opposing Choice Scarf Shaymin-S will beat you.
There are also several leads that will almost always beat Shaymin-S. A Choice Scarf Mewtwo will outspeed Shaymin-S, and can OHKO it with Ice Beam. Although Kyogre may be weak to Seed Flare, a 252 HP Kyogre lead will always survive it, and then OHKO Shaymin-S with Ice Beam. Lead Dialga can take an Earth Power, and then OHKO Shaymin-S back with Draco Meteor. Scizor leads can also give Shaymin-S that lack Hidden Power Fire trouble, as it is 3HKOed by Bullet Punch. Tyranitar leads can take a Seed Flare thanks to the sandstorm Special Defense boost, and OHKO Shaymin-S with Stone Edge. Blissey can be a good partner for a lead Choice Scarf Shaymin-S, as it can easily wall lead Kyogre, Dialga, and Mewtwo. Groudon can switch into Tyranitar’s Stone Edge, and OHKO most with Earthquake, while Scizor will take a severe amount of damage, or will be OHKOed by a Fire-type attack. Although Draco Meteor will do a huge amount of damage to Groudon, the thought of STAB Earthquake will often scare Dialga off. While Palkia and Latias can destroy Kyogre, be warned that several lead Kyogre carry Thunder Wave to take advantage of these switch-ins. A Dialga of your own can switch into Mewtwo, Kyogre, and Scizor, and can threaten them with Draco Meteor, Thunder, and Fire Blast respectively.
