Moves

• Transform is the only legal move Ditto can learn. However, it is mostly useless due to Imposter activating upon Ditto switching in, and if Imposter fails, then Transform would as well.

Set Details

• Imposter is what makes Ditto viable, allowing it to copy the opposing Pokemon and all its stat changes.
• A Choice Scarf is essential for Ditto to perform its role as a revenge killer, allowing to outspeed any Pokemon it copies, unless both carry Choice Scarf or Trick Room is active.
• 248 HP EVs maximize Ditto's HP while minimizing Struggle recoil.
• 252 Defense EVs and 0 Speed IVs with a Relaxed nature minimize damage taken from an opposing Ditto's Struggle and lower Ditto's Speed so it hopefully moves after opposing Ditto to avoid being the first to KO itself with Struggle damage.
• The given IV spread gives Ditto Hidden Power Ice, granting it optimal coverage when copying opposing mixed Primal Groudon and Marshadow should they be carrying Hidden Power. This potentially allows Ditto to pick off Mega Salamence and Zygarde-C should it try to switch in.
• The remaining EVs are invested into Attack to slightly boost the power of Ditto's Struggle.

Usage Tips

• Use Ditto to revenge kill threatening boosted sweepers, such as Rock Polish Primal Groudon and Geomancy Xerneas.
• It is safest to bring Ditto into play after a teammate has fainted or through slow pivots. Without the latter, Ditto only has so many opportunities to switch into threats that it is relied on to revenge kill, often at great cost to its team, so it must carefully select what move it uses to make the most of each time it comes into play.
• Although switching directly in on Pokemon that can KO Ditto, such as Primal Groudon, is extremely risky, it may sometimes be necessary in order to avoid giving too much ground to the foe. Pivoting with teammates that discourage the use of moves that Ditto cannot switch in on can make such a play much safer. For example, Primal Groudon will be hesitant to use Precipice Blades against a Pokemon immune to Ground-type attacks or a Zygarde that will activate Power Construct if hit, potentially opening up an opportunity for Ditto to switch in.
• Ditto is often forced to lock into a specific move in order to revenge kill a foe, and thus Pokemon that can safely switch into that move can deny Ditto from being able to revenge kill its foe. As Ditto will likely have had to switch in after a teammate has fainted, this means its team has lost a valuable member for little in return if Ditto fails to claim a KO. This may force Ditto to use a risky coverage move to target the switch-in instead of revenge killing in order not to cede too much momentum.
• If all else fails, Ditto can function as a wincon, using its teammates as fodder in order to obtain as many free switches as possible. If this is the case, aim to target Pokemon on the opposing team that can wall a Choice-locked Ditto, either by wearing them down or by removing them with teammates, or use Ditto to nail them with coverage moves as they come in.
• Foes that can survive an attack from Ditto and OHKO it in return thanks to the difference in the HP stat or the power from a boosting item will need to be weakened in order for Ditto to effectively revenge kill them. Examples include Life Orb Marshadow and Ultra Necrozma without Outrage.
• Thanks to Imposter, Ditto ignores the Speed drop from Sticky Web, making it a great revenge killer against common Sticky Web sweepers.
• Ditto is unable to effectively revenge kill Trick Room sweepers, such as Swords Dance + Trick Room Necrozma-DM, as they outspeed Ditto during the duration of Trick Room and can KO it before it can attack. In the case of Necrozma-DM, it can even survive a boosted Earthquake if Ditto switches in as Necrozma-DM uses Swords Dance and sets up Trick Room before KOing Ditto. Attempt to take on such foes with other teammates when Trick Room is active or stall out Trick Room turns until the effect is over so Ditto can outspeed its foe once again.
• Ditto can switch into defensive foes, particularly those with reliable recovery and without status moves that can afflict Ditto, and proceed to stall them out to gain a PP advantage thanks to its PP refreshing each time it switches out. Notable targets that Ditto can wall include support Arceus without Toxic, Mega Sableye, and Blissey.
• Ditto can also come in on foes with support moves such as Heal Bell and Defog and take advantage of these moves to support its team without wasting any PP.
• Ditto can only effectively stay in for five turns at a time, after which it will be forced to use Struggle unless it has lost its Choice Scarf.
• Ditto can be used to scout the moveset of the opponent's Pokemon.
• Imposter's potential greatly expands the number of possible plays in-game depending on the opponent's Pokemon and movesets, so keep an eye out for creative ways you can use it.

Team Options

• Ditto can round off a mostly complete team looking for a revenge killer to deal with a range of threats that cannot be walled by a single Pokemon. Thus, a solid defensive backbone to deal with most relevant threats should be present with Ditto, as it relies on its teammates to switch into offensive foes. In return, they appreciate Ditto's ability to revenge kill any threats that may break through.
• On the other hand, Ditto can round out a frail offensive team that has little defensive synergy and relies on overwhelming offensive pressure to win or a specialized team that is dependent on executing a specific niche strategy and is thus unable to defensively cover many prominent threats. Ditto can function as a safety net should an opposing setup sweeper manage to set up, and it can also simply discourage the use of setup moves from the opponent altogether.
• Support Arceus formes, such as Arceus-Fairy, as well as Arceus-Ground, Arceus-Water, and Arceus-Dark carrying Ice Beam, can take on Dragon Dance Zygarde-C in particular, which Ditto finds difficult to effectively revenge kill thanks to Substitute. Additionally, they check a plethora of other threatening offensive Pokemon that Ditto cannot reliably handle; Arceus-Fairy checks Marshadow and Yveltal, Arceus-Dark checks Yveltal and Ghost- and Psychic-types, Arceus-Ground checks Primal Groudon and Necrozma-DM, and Arceus-Water can take on the latter two in addition to Ho-Oh. All four of them also check Mega Salamence and Rayquaza. Another option is Choice Scarf Xerneas, which can function as a more offensive check to Zygarde-C. In return, Ditto can take on setup sweepers that support Arceus formes and Xerneas often cannot, such as Swords Dance Primal Groudon and Double Dance Necrozma-DM.
• Physically defensive walls such as defensive Zygarde-C carrying Coil, Skarmory, Mega Sableye, and both Giratina formes can wall most Swords Dance Arceus formes, which can pose trouble for Ditto if they are carrying Substitute. On more offensive teams, Marshadow is an option to deal with Swords Dance Arceus behind a Substitute. Zygarde-C and Giratina can also deal with offensive Ho-Oh and Primal Groudon to varying extents, while Skarmory, Mega Sableye and Marshadow can help against Ultra Necrozma. All of them can also assist taking on Necrozma-DM, and they appreciate Ditto's ability to deter opposing setup sweepers that they cannot handle.
• Blissey and, to a lesser extent, Magearna, Necrozma-DM, Ho-Oh, and Primal Kyogre, can either wall or overpower Calm Mind Arceus formes for Ditto. All of them except Primal Kyogre can also switch into various threatening special attackers like Geomancy Xerneas. Blissey and Magearna can additionally provide cleric support with Heal Bell, while Magearna can also help Ditto find safe opportunities to come into play with Volt Switch. In return, Ditto can deter physically oriented wallbreakers from using Ditto's specially defensive teammates as setup fodder.
• Entry hazard setters can allow Ditto to use the threat of a revenge kill to rack up hazard damage on checks to Ditto's current transformation in an aggressive fashion, potentially paving the way for an Imposter sweep. Primal Groudon, Ferrothorn, Skarmory, and support Arceus formes can provide entry hazard support in addition to checking prominent offensive threats such as Primal Kyogre and Necrozma-DM.
• Klefki is another option, which, in addition to setting Spikes, can blanket check offensive threats alongside Ditto by inflicting Prankster-boosted status. Klefki can also opt for Swagger, which synergizes well with Ditto by allowing it to copy the foe's Attack boosts, and can even use Fairy Lock to guarantee that Ditto revenge kills any target that KOes Klefki with the right timing.
• Defog and Magic Bounce users such as Ho-Oh, both Giratina formes, support Arceus formes, and Mega Sableye can keep Ditto's side of the field clear of hazards, preventing it from getting chipped each time it switches in. Ditto can support such teammates in the hazard war by potentially copying support moves like Stealth Rock, Defog and Heal Bell.
• Yveltal and Mega Scizor can potentially provide Ditto opportunities to switch in with U-turn, with the latter being able to lure in Primal Groudon so Ditto can copy it and threaten it out with its own super effective STAB move. Ditto can return the favor, as it commonly transforms into Pokemon that draw out resisted moves for Yveltal and Mega Scizor to switch into, such as Ground- and Steel-type moves targeted at Primal Groudon and Xerneas, respectively.
• Wallbreakers and other Pokemon strong against defensive teams can partner well with Ditto on more balanced or offensive teams to complement Ditto's strong matchup against offensive threats. Examples of powerful wallbreakers include mixed Swords Dance Primal Groudon, Calm Mind Primal Kyogre, Calm Mind Lunala, and Bulk Up Marshadow. Despite their lack of immediate power, stallbreaker Yveltal and Substitute + Dragon Dance Zygarde can also pose large issues for bulkier teams. Finally, Gothitelle can trap and remove key members of more defensive teams.