Dialga’s unique typing and well-distributed stats make it both an excellent offensive and defensive Pokemon. Offensively, Dialga has a stunning base 120 Attack and base 150 Special Attack that's backed by the ever-dominant Dragon-type STAB. Dialga's vast offensive movepool allows it to pick off a variety of Pokemon. Defensively, Dialga’s typing offers it a whopping total of nine resistances and an immunity, as well as neutrality to Ice- and Dragon-type attacks, something other Dragon-type Pokemon would kill for. With its stellar base defenses combined with the aforementioned resistances, Dialga is a difficult Pokemon to take down unless you target its weaknesses. Dialga is also revered as an excellent utility Pokemon thanks to its equally-vast support movepool. With its plethora of options, Dialga is, in a word, unpredictable.
STAB Draco Meteor bolstered by 438 Special Attack, or 399 if Dialga opts to use a Hasty nature, is frightening for any opponent. Only Steel-type Pokemon and Blissey can take Draco Meteor without the risk of being 2HKOed in the process, though some frailer Steel-types such as Lucario take major damage anyway (66.2% - 77.9% if Dialga is Mild). Brick Break, with the given Attack EVs, will 2HKO most Uber Blissey with Stealth Rock in play. Fire Blast is the best attack for taking down the vast majority of Steel-types in the Uber metagame, but it comes with the downside of being weakened by the near-omnipresent rain. This can be resolved by partnering Dialga with Groudon or Tyranitar. The final slot should generally be Thunder due to its perfect accuracy in the rain; with its 30% chance of paralysis, most opponents will think twice before they switch in, since many Dialga checks or counters rely on their Speed. Outrage is an excellent attack to use with or without Bulk Up. Without Bulk Up, Dialga can use Outrage with a Life Orb to 2HKO most Kyogre and Blissey. Bulk Up is a great lure move since it draws in Groudon, which is in turn shut down by STAB Draco Meteor. With Bulk Up, Dialga should be able to even surge through Wish Blissey.
To maximize Dialga’s potential, there are many options in regards to natures and EVs. The suggested EV spread and nature allows Dialga’s Draco Meteor to hit with maximum power and outspeed Adamant Scizor. 144 Atk EVs grant Dialga the ability to 2HKO most Blissey, barring max HP / max Def variants. If you opt for Mild, you should use Expert Belt, since it provides enough power to obtain the same KOs as Life Orb while conserving Dialga’s HP. Hasty, with 64 Atk / 252 SpA / 192 Spe EVs, allows Dialga to outspeed Adamant Rayquaza and Adamant Lucario. Hasty with 4 HP / 252 SpA / 252 Spe also works. Outspeeding Adamant Rayquaza means that Dialga’s team is less susceptible to a Swords Dance Rayquaza sweep, though keep in mind that most Dragon Dance and Mixed Rayquaza sets use a positive Speed nature. With a Hasty nature, Dialga will need a Life Orb in order to stay competitive offensively. Because Dialga can survive Choice Scarf Garchomp's Earthquake and even Life Orb Aura Sphere from Mewtwo, Dialga can effectively utilize a spread of 120 HP / 136 Atk / 252 SpA with a Quiet nature in order to survive one of those assaults. Expert Belt is preferable for Quiet Dialga since the main goal is to make sure that Dialga is as healthy as possible in case it needs to take these extreme hits. Life Orb can be used, however, since Dialga can even OHKO Support Groudon with Draco Meteor 100% of the time with a Quiet nature, which is slightly reduced to 87% with Hasty; Stealth Rock and a layer of Spikes assures the KO. Life Orb Outrage also 2HKOes max HP / min Def Kyogre, which means Dialga can be effective at taking out Mono-Attacker Kyogre. Brick Break, with Stealth Rock in play, can also be used to easily 2HKO Heatran, since max HP / min Def variants takes 43-50.8%.Team Options & Additional Comments >>>
This set takes advantage of Dialga’s numerous resistances, well-distributed defensive stats, access to a STAB attack that only has one resistance, and Bulk Up. Bulk Up boosts Dialga’s Attack and Defense stats, which helps power up its Dragon-type attack of choice, as well as increase its chances of survival against physical attacking Pokemon. For example, after a Bulk Up, Dialga can survive Choice Band Garchomp's Earthquake. Once Dialga finds an ideal time to do so, simply Rest off the damage, all the while using Sleep Talk to keep Dialga threatening to the opponent. This set is excellent for absorbing Dark Void from Darkrai since Dialga isn’t deterred by falling asleep. Outrage versus Dragon Claw is a matter of preference between power and reliability. Since Dialga will be boosting its Defense via Bulk Up, max Special Defense is necessary to help Dialga cushion special attacks.Team Options & Additional Comments >>>
Dialga is unique amongst its Dragon-type cousins because it can play a supporting role effectively. Stealth Rock requires no real explanation, though keep in mind that Dialga should lay down Stealth Rock as soon as possible to prevent Ho-Oh from switching into Dialga freely. The next move is dependent on the type of team that Dialga is supporting. An offensive team appreciates Thunder Wave more than Toxic since the paralysis of threats such as Mewtwo, Darkrai, and Choice Scarf Pokemon is a significant advantage. On the other hand, defensive teams require Toxic to make sure that the opponent’s team won’t out-stall Dialga’s team, since Lugia, Giratina-O, Latias, and the rare Cresselia are all unaffected by Toxic Spikes. Draco Meteor can be used to limit the number of times Groudon can switch freely into this set, while Dragon Pulse offers consistency that keeps Dialga on the field without being a detriment offensively. Flamethrower helps keep Forretress and other Steel-types, barring Dialga and Heatran, from switching into Toxic freely. Thunder works best alongside Kyogre as its Drizzle ability remedies Thunder’s poor accuracy. Thanks to the 30% chance of paralysis, Dialga can operate as a pseudo-double status spreader, since it is free to use Toxic instead of Thunder Wave. Though not mentioned on the set, Roar can be used over the second or fourth moveslot. The reason that Roar can replace a status move is that, assuming Dialga is on a stall team, Toxic Spikes will be already taken care of by one of Dialga's teammates. Since Lugia and Cresselia are the only general threats against Dialga that are immune from Toxic Spikes, Roar can be used to prevent these Pokemon from taking advantage of Dialga. Furthermore, there are likely better teammates that can handle Lugia and Cresselia such as Tyranitar.
The given EVs ensure that an unboosted Timid Kyogre's Water Spout will not 2HKO Dialga. This allows Dialga to Thunder Wave, Stealth Rock, and then switch to the appropriate counter. The Special Attack EVs and Modest nature allow Dialga to always OHKO Darkrai with Draco Meteor, and to always OHKO Palkia with Dragon Pulse after it switches into Stealth Rock once.Team Options & Additional Comments >>>
Dialga’s lackluster Speed can be fixed with the item Choice Scarf at the cost of locking Dialga onto one attack. Dialga reaches 459 Speed with Choice Scarf, which is enough to outspeed Deoxys-A. Draco Meteor is the primary attack; with Stealth Rock in play Draco Meteor easily OHKOes Darkrai, and has a 33% chance of OHKOing Mewtwo. Thunder is used to 2HKO Lugia after Stealth Rock, and for inflicting severe damage onto Kyogre. Fire Blast can be used to prevent Steel-types from switching in freely, but it relies more on the team having dual weather to support both it and Thunder. Aura Sphere can help reduce the chances of a Lucario and Dialga sweep, while nailing Heatran and Tyranitar for super effective damage. For the fourth moveslot, Dragon Pulse gives Dialga a move that is consistent damage-wise. On the other hand, Outrage, with a Hasty nature, can be used to take down Calm Mind Kyogre; it may also get the 2HKO on Blissey.Team Options & Additional Comments >>>
If you thought Dialga's meteor showers were already painful enough, then just wait until you see what happens when they are boosted by Choice Specs! Not only does Draco Meteor OHKO Groudon, barring those that heavily invest in Special Defense, but it has enough power to OHKO Lucario. Even max HP Metagross has an 87% chance of being 2HKOed by Draco Meteor. Thunder helps Dialga a lot since the paralysis caters to Dialga’s low Speed. After Stealth Rock, Thunder also OHKOes max HP Kyogre. Fire Blast is used to prevent wasting Draco Meteor's PP on Steel-type Pokemon, while decreasing the chances of Groudon safely switching into Dialga. Since Heatran can cause trouble with its resistance to Dialga’s Dragon-type attacks, Aura Sphere can be used instead. Aura Sphere is also an option over Thunder since Draco Meteor hits hard enough to OHKO min HP Kyogre anyway.
The given EVs allow Dialga to outspeed max Speed Adamant Tyranitar. They also keep Dialga very bulky so it can keep threatening the opponent. If you want Dialga to be faster, you can use 112 Speed EVs to outspeed Adamant Scizor, or max Speed to outspeed the vast majority of bulky 90 base Speed Pokemon, while tying with those that attempt to be agile. Timid is also a good nature since it allows Dialga to outspeed Adamant Rayquaza, while tying with max Speed Jolly Lucario. Dialga can use 192 Speed EVs with a Timid nature to outspeed said Adamant Rayquaza and place the rest of the EVs toward HP.Team Options & Additional Comments >>>
Although it may seem strange to use Trick Room on a Pokemon with Base 90 Speed, Dialga is relatively slow by Ubers standards, which can actually let Dialga sweep if it sets up. With a Quiet nature and the listed IVs, Dialga reaches 166 Speed, which allows it to outpace virtually every common threat in Ubers when Trick Room is active. Since Dialga has no use for Speed EVs, it can maximize both its Attack and Special Attack, allowing it to abuse two powerful STAB attacks: Draco Meteor and Outrage. With a Life Orb boost, Dialga functions as a powerful wallbreaker, as it can simultaneously nail both physical walls and special sponges such as Groudon and Blissey, respectively. The final slot is dedicated to hitting Steel-types that resist Dialga's powerful Dragon-type attacks. Fire Blast will roast most Steels in the sun, but Earthquake is a suitable alternative if you want to be able to effectively damage Steel-types in the rain, while also allowing Dialga to easily KO Heatran. Earthquake also isn't weakened if Draco Meteor has been previously used.Team Options & Additional Comments >>>
Finally, a set other than Bulk Up that doesn’t call for the spamming of Draco Meteor! With this set, Dialga forgoes special attacks in order to catch many of its switch-ins off-guard. Don’t assume that Groudon has the upper hand against this set; unless Groudon invests heavily in its Defense stat, it is 2HKOed by Outrage. Earthquake complements Outrage by giving Dialga a wide amount of coverage against the Uber metagame; it prevents most Steel-types, especially Heatran, from switching in safely. Dragon Claw should be your third move as Outrage lock puts Dialga in grave danger if you’re not aware of the rest of the opponent's Pokemon. The fourth move depends on whether you prefer shutting down the majority of Steel-types, notably Skarmory, or annihilating Ho-Oh and keeping Lugia away from Dialga.
The EV structure is very similar to the Choice Specs set, with the only difference being not recommending a positive Speed nature. Outspeeding Adamant Tyranitar is the minimum amount of Speed Dialga should use. You can opt to use 116 Speed EVs to outspeed Adamant Scizor, or max Speed to tie with Adamant Lucario or Modest Kyogre at worst. Jolly nature with max Speed and max Attack allows Dialga to get the upper hand on Adamant Rayquaza at the cost of sheer attacking power.Team Options & Additional Comments >>>
Dialga has loads of other options that can work as potential support moves. Psych Up can be useful on Dialga, allowing it to copy the stat boosts that Calm Mind Kyogre may have netted. Dialga is a great user of Trick Room in Ubers too, having brilliant all-around stats bar Speed. Flash Cannon is an auxiliary STAB attack, but Steel is a poor offensive type. Ice Beam with Choice Specs allows Dialga to OHKO Groudon without resorting to Draco Meteor or Overheat, but is otherwise generally a poor choice. Iron Tail should be avoided, because as already noted, Steel is a poor offensive type, and its 75% accuracy leaves much to be desired.
Magnet Rise can be a good option on some Dialga sets, as it can foil Dialga's arch enemy, Groudon. If you opt for Bulk Up with Magnet Rise, then use the EV spread of 116 HP / 252 Atk / 140 Spe. This allows Dialga to Bulk Up as Groudon switches in, use Magnet Rise before most Groudon can move, and then either hit the next switch-in hard with Outrage or Earthquake, or use Bulk Up again.
Roar of Time sounds and looks cool, but is in fact a terrible move to use, as is the rest of the Hyper Beam suite; Draco Meteor and even Dragon Pulse out-damages it over the course of two turns, and the unavoidable second turn recharge is a perfect opportunity for something threatening to set up. As for items, Choice Scarf can be used with physical moves if so desired, but without the extra power of Choice Band, the attacks will be too weak to be useful.
252 HP / 116 SpD with a neutral nature allow Dialga to never be 2HKOed by Kyogre's Choice Scarf Water Spout, provided Dialga holds Leftovers. 252 HP / 44 Def, again with a neutral nature, will allow Dialga to never be 2HKOed by Mewtwo's Life Orb Brick Break, or OHKOed by its Focus Punch.
Checks and Counters
Simply put, Dialga is hard to counter. How it can be countered depends a lot on the weather conditions and the moveset it is using. In general, Ho-Oh and Heatran can counter Dialga while under sunny conditions. The biggest thing to note is that Thunder’s accuracy is cut to 50% under the sun, which means a 15% chance that Ho-Oh and Heatran will be hit by Thunder followed by paralysis. Meanwhile, Ho-Oh’s Sacred Fire has a 50% chance to inflict a burn on Dialga, which hampers the Mixed and Choice Band sets. With Ho-Oh’s access to recovery, Pressure, and a high Special Defense stat, Dialga is in trouble when it only has Stone Edge to kill Ho-Oh. Heatran can shut down the Bulk Up set with a simple use of Taunt, while fearing only Earthquake or Aura Sphere at worst from Dialga. If rain is present, then a more cautious approach to countering Dialga is necessary, as a 30% chance of paralysis from Thunder is nothing to scoff at. Scizor comes relatively close as a counter since Fire Blast is weakened in the rain, while Scizor can fire off Superpower at Dialga for super effective damage. Metagross can step into the scene and fire off Earthquake at Dialga, or use Trick on sets such as Bulk Up or Support to cripple Dialga. It also does well at countering the Choice Band set, though beware of stepping into either Earthquake or Overheat in the sun.
Groudon is a good counter since it threatens Dialga with STAB Earthquake, and has access to Roar to nullify the Bulk Up set. Offensive Groudon has an easier time KOing Dialga since many opponents opt to use a -Def nature on Dialga's mixed set. Blissey can take on both the Specs set and the Scarf set, though beware that the Scarf set can carry Outrage to try to 2HKO Blissey. Skarmory does well at countering the physical Dialga sets, especially the Bulk Up set which has no answer against Skarmory, except if Skarmory and Dialga are the last Pokemon standing. Lugia has to avoid switching into Stone Edge and Thunder at all costs, but it is otherwise a great counter to Dialga while the sun is out. It can set up Reflect to deter the Choice Band set, while Whirlwind deals with the Bulk Up set. Tyranitar, especially those that invest in Special Defense, can be a great Dialga check when Tyranitar is at full health. Wobbuffet can be an annoying Pokemon for Dialga to deal with, since Dialga lacks Taunt or a powerful enough move to OHKO Wobbuffet on the spot. It has to beware of the Mixed set when Draco Meteor is at full power though.
Since Dialga is a slow Pokemon, you can use faster Pokemon to revenge kill it. This strategy fails when Dialga carries a Choice Scarf, but it is still the safest way of dealing with most Dialga sets. Latios using Dragon Pulse does 48.5% - 57.4% on Support Dialga, which means Latios 2HKOes non-Bulk Up Dialga without relying on Draco Meteor 93% of the time. Latias can switch in safely after Dialga has expended a Draco Meteor and start setting up Calm Minds. Life Orb Mewtwo's Aura Sphere can OHKO min HP / min SpD Dialga 43% of the time while Specs Aura Sphere will always OHKO. Deoxys-A has access to Superpower to obliterate Dialga on the spot, as it does around the same damage as Mewtwo's Choice Specs Aura Sphere. Garchomp has access to STAB Earthquake to make sure Dialga doesn't stay in comfortably. Darkrai can use Dark Void to nullify every set barring the Bulk Up set, while OHKOing Dialga with a Nasty Plot-boosted Focus Blast.