[Overview]
<p>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. Its Dialga's vast offensive movepool allows Dialga  it  to pick off those that either resist its Dragon-type STAB, or are  capable of cushioning the damage, with relative ease a variety of Pokemon. Defensively,  Dialga’s typing offers it a whopping total of 9 nine resistances and an  immunity, while still being neutral as well as neutrality to Ice- and Dragon-type attacks, (comma)   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.</p>
[SET]
name: Mixed Dialga (redundant; we'd be saying Support Dialga, etc.)
move 1: Draco Meteor
move 2: Outrage / Brick Break
move 3: Fire Blast
move 4: Thunder / Bulk Up
item: Expert Belt / Life Orb
nature: Mild / Hasty
EVs: 144 Atk / 252 SpA / 112 Spe
[SET COMMENTS]
<p>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 anyhow 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 without losing to 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.</p>
<p>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. The 144 Atk EVs allow 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 majority of 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. Finally, Because Dialga can survive  Choice Scarf Garchomp's Earthquake or and even a Life Orb Aura Sphere from  Mewtwo; because of this, Dialga can effectively utilize a spread of 120  HP / 136 Atk / 252 SpA with a Quiet nature (is the surviving part with the ev spread? might want rewording if so). 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 Mild (both increase SpA; did you mean 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%.</p>
[ADDITIONAL COMMENTS]
<p>A couple of move options were left out of the set because they   only offer niche results, but are nevertheless effective choices if   Dialga needs them. Earth Power means Dialga will never fall to a Heatran   switch-in, while still being able to damage other Dialga regardless of the  weather (wouldn't you Draco Meteor other Dialga instead of Fire Blast?).  Stealth Rock is also an option since Dialga forces many  switches.  Finally, Stone Edge can be used if Dialga’s team has issues  with Ho-Oh.  While Draco Meteor and Outrage do sufficient damage by  themselves,  Draco Meteor has the nasty drawback of -2 SpA while Pressure  takes away  2 PP in the process. Outrage is risky since Ho-Oh's  Sacred  Fire has a 50% chance of a burn behind it, and usually has  boosted power  thanks to most Ho-Oh being used in conjunction with  sunlight. These  moves can replace either Thunder or Fire Blast. For  items, Leftovers and  Adamant Orb are viable. Leftovers offers Dialga  recovery and works well  with the Quiet spread, while Adamant Orb helps  bluff Choice  Specs.</p>
<p>While Dialga is an intimidating Pokemon, it does require   support from its teammates. As shown with just a few damage   calculations, Dialga appreciates entry hazards to help it net its KOs.   Leads such as Deoxys-S or Deoxys-A are great choices for teammates since   they have a high chance of getting Stealth Rock and at least one layer   of Spikes up. Forretress is also a great partner as it has the added   benefit of removing entry hazards on your side of the field thanks to   Rapid Spin. Giratina-O can also be a staple provided that you’re using   entry hazards. (period) though It  has the added benefit of being able to handle  Groudon well thanks to  its Earthquake immunity and moderate base  defensive stats. Since  Thunder is reliant on rain, Kyogre is an  excellent partner, as not only  does its ability boost Thunder’s accuracy  to 100%, but it  also nullifies Heatran as a threat while making Ho-Oh less  effective,  thanks to Dialga resisting Brave Bird. Sadly, Groudon doesn’t  bring as  many benefits to the table as Kyogre does, though Support  Groudon is an  excellent teammate as it can slow Dialga’s counters down  with Thunder  Wave while being able to set up Stealth Rock. Since Dialga  is great at  breaking through defensive teams in general, offensive  Pokemon such as  Dragon Dance Rayquaza and Swords Dance Garchomp  appreciate having  Dialga as their partner.</p>
<p>Dialga’s other issues involve its lack of Speed, which leaves   it susceptible to being revenge killed by Pokemon such as Mewtwo  or and  Latios. Scarf Garchomp is a great partner since it outspeeds Dragon  Dance Rayquaza and Scarf Palkia. Another great Scarf user is Shaymin-S, (comma) which  can target both Kyogre  and Groudon with STAB Seed Flare while  outspeeding Rock Polish Groudon.  Scarf Tyranitar is rather slow;  however, its natural bulk and SpD boost  from the sandstorm allows it to  be effective at revenge killing  non-Dragon Dance Rayquaza, Latias,  Latios, Swords Dance Lucario,  Heatran, and Ho-Oh. While Wobbuffet is  slower than Choice Scarfers, it  has the advantage of being able to  cushion at least one hit from a Scarf  Pokemon before biting the dust.  Finally, Heatran does very well at  stopping a Mixed Dialga sweep cold,  so teammates are needed to handle  this situation. While Kyogre has already been mentioned as a good  Heatran check, Calm Mind Latias does very well is great at switching into  Heatran’s attacks due to its great special bulk and resistance to Fire.  It only fears Taunt and Explosion, the latter being  rare on bulkier  Heatran to begin with. Rayquaza’s Air Lock nullifies the  sunlight’s  boost, and it can switch into Earth Power freely, though it  has to be  careful with Dragon Pulse variants.</p>
[SET]
name: Defensive Bulk Up
move 1: Bulk Up
move 2: Outrage / Dragon Claw
move 3: Rest
move 4: Sleep Talk
item: Leftovers
nature: Careful
EVs: 252 HP / 4 Atk / 252 SpD
[SET COMMENTS]
<p>This set takes advantage of Dialga’s numerous resistances,  well-distributed defensive stats, and access to a STAB attack that only  has one resistance going against it, (comma) and Bulk Up. Bulk Up boosts Dialga’s Attack and  Defense stats, (comma) to help 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 a 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,  respectively.  Since Dialga will be boosting its Defense via Bulk Up, max  Special  Defense is necessary to help Dialga cushion special  attacks.</p>
[ADDITIONAL COMMENTS]
<p>Skarmory, Lugia, Groudon, Heatran, and Lucario to some extent will cause  issues for this set. The best way to address this these threats is to have Pokemon  that are offensively-oriented as  offensively-oriented   teammates for Dialga. While it will  need Aura Sphere to deal with  Heatran, Giratina-O stops most Groudon  sets cold thanks to STAB Draco  Meteor and its immunity to Earthquake.  Mixed Rayquaza is also an  excellent teammate, since it lures in and  takes out many of Dialga’s  checks, and doesn’t require any setup time to  do so. Rayquaza needs to  be more aware of its surroundings, sadly however,  since switching into any of Dialga's counters will leave your Rayquaza  crippled or likely fainted. While Mixed Attacking  Dialga could check  many of its slower enemies with the help of some  Speed EV investment or  even a Hasty nature, this set has many problems  with Pokemon that are  faster than  it. Some of the recommended Scarf Pokemon mentioned in the Mixed Attacker   set (Shaymin-S and Garchomp for example) are great assets since  Groudon likely outspeeds Dialga with the given EVs.</p>
<p>Sadly, some of the problematic  Pokemon that Dialga faces cannot be  exactly "countered" per se, but  they should definitely be brought to  attention while you plan out  Dialga's setup. Wobbuffet can cause some  issues with this set in  particular. Wobbuffet It can easily Encore a move  and not take damage three-fourths of the time, or two-thirds of the time  while if Dialga is asleep and locked onto Sleep Talk. Assuming Stealth  Rock, Dialga would need 3 three Bulk Ups in order to come close to nearly KO Wobbuffet range (80.7% - 95.1%) with Outrage (80.7% - 95.1%). With Dragon Claw, Dialga needs 3 three  Bulk Ups in order to  2HKO Wobbuffet. Since there is no real way of  countering Wobbuffet, the  best that can be said is “Watch out”. Haban Berry  Garchomp cannot always win  against this set, but it can either  severely damage Dialga or scare it  off. Even after a Bulk Up, a Swords  Dance-boosted Earthquake from  Garchomp will OHKO Dialga 87% of the  time. Taunt is uncommon, but it is a  relevant threat since it allows Pokemon such as Mewtwo to set up Calm Minds  freely when  Dialga is asleep. Finally, watch out for Trick; since many  Pokemon in  the Uber metagame are part Psychic-type, it is a common  move to have on  Choice sets.</p>
[SET]
name: Support
move 1: Stealth Rock
move 2: Toxic / Thunder Wave
move 3: Draco Meteor / Dragon Pulse
move 4: Flamethrower / Thunder
items: Leftovers
nature: Modest
EVs: 252 HP / 140 SpA / 116 SpD
[SET COMMENTS]
<p>Dialga is unique amongst its Dragon-type cousins (removed semi-colon) 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  of choice 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 works best to helps (Thunder did this)  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(space)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 the 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 (backspace this). Since Lugia and Cresselia are the only general threats  against Dialga and that are immune from Toxic Spikes, Roar can be used to  prevent these Pokemon from taking advantage of Dialga to set up.  Furthermore, there are likely better teammates that can handle Lugia and  Cresselia (such as?).</p>
<p>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.</p>
[ADDITIONAL COMMENTS]
<p>This set can also be used as a lead. The only change needed is   Lum Berry as the item and Thunder Wave as the status move. Lum Berry is   used to prevent Dialga from being put to sleep by Darkrai leads,   allowing Dialga to severely cripple them with Thunder Wave. Dialga is, (comma)  however, (comma) unable to prevent Deoxys-S and Deoxys-A from setting up Stealth  Rock and possibly a layer of Spikes.</p>
<p>Dialga, (comma) on a stall team, (comma) would appreciates the residual damage  from Spikes and/or  Toxic Spikes. Forretress is the best Pokemon for  laying down Toxic  Spikes in the Uber metagame. This lessens the need for  Toxic since the  only Pokemon that Toxic Spikes will miss are Levitating  and Flying-type Pokemon, and some of them can be disposed of removed  by  Dialga’s Draco Meteor or Dragon Pulse. Forretress can also lay down   Spikes, but relying on it to lay down all three layers of Spikes and  two  layers of Toxic Spikes puts Forretress under a lot of stress. As a   lead, Deoxys-S can set up Spikes, since it can forgo Stealth Rock if   Dialga opts to use it. Skarmory is an excellent Pokemon in this   situation, since it completely walls Groudon barring the rare Overheat,   can set up Spikes, has access to a recovery move, and can use Whirlwind   to force switches. With entry hazards taken into account, Dialga needs  a  teammate that can block Rapid Spin. Giratina-O is the best Pokemon  for  the job.</p>
<p>Offensive teams appreciate Stealth Rock and Thunder Wave or   Toxic support. Rayquaza, for example, has an easier time crushing teams   if most of the opponent’s Pokemon is slower than it. With Toxic   crippling defensive Pokemon, Swords Dance Lucario has an easier time   sweeping the opponent. Offensive Groudon loves Support Dialga since many   of its checks can be battered by Dialga. Swords Dance Groudon climbs  in  effectiveness with Thunder Wave support, while Rock Polish Groudon  is  solid with Toxic support.</p>
[SET]
name: Choice Scarf
move 1: Draco Meteor
move 2: Thunder
move 3: Fire Blast / Aura Sphere
move 4: Dragon Pulse / Outrage
item: Choice Scarf
nature: Timid / Hasty
EVs: 4 HP / 252 SpA / 252 Spe
[SET COMMENTS]
<p>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 be used to 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 is in the fourth  moveslot to gives Dialga a move that is consistent damage-wise. On the other hand, Outrage,  with a Hasty nature, can be used to help Dialga take down Calm Mind  Kyogre; it may also get the 2HKO on Blissey.</p>
[ADDITIONAL COMMENTS]
<p>Dialga can use a Modest or Mild nature if you want more power   behind Dialga’s attacks.  The advantage of outspeeding Dragon Dance   Rayquaza may be lost with this set change,  since many of them opt to run a  Jolly nature. With Modest, Dialga  OHKOes Mewtwo after Stealth Rock 87%  of the time.</p>
<p>Scarf Dialga can handle some walls with careful prediction, but   above all else Dialga wants some weather to help it take advantage of   Thunder and possibly Fire Blast. Offensive Kyogre and Groudon both   appreciate faster Pokemon being picked off by Dialga. Scarf Dialga may   be quick, but it does lose to Scarf Palkia, Scarf Garchomp, (comma)  and Scarf  Darkrai in Speed. Groudon can handle Scarf Garchomp and  Scarf Palkia  most of the time, though beware that continuously taking  damage will  eventually wear out Groudon due to its lack of recovery.  Scarf Darkrai’s  only threatening attacks are either Dark Void or and Focus Blast, the  latter having only 70% accuracy. Scizor can switch into Scarf Darkrai  safely and OHKO it with U-turn. Scizor It can at least take out a weakened  Darkrai with Bullet Punch if necessary (54.4% - 64.4%). Finally, (comma) be very cautious  of Wobbuffet as it can revenge kill Dialga easily thanks to the Choice  lock.</p>
[SET]
name: Choice Specs
move 1: Draco Meteor
move 2: Dragon Pulse
move 3: Thunder
move 4: Fire Blast / Aura Sphere
item: Choice Specs
nature: Modest
EVs: 224 HP / 252 SpA / 32 Spe
[SET COMMENTS]
<p>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 (backspace this).  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.</p>
<p>The given EVs allow Dialga to outspeed max Speed Adamant  Tyranitar. This They also keep Dialga very bulky so it can keep threatening the opponent, making it a very potent  threat to 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.</p>
[ADDITIONAL COMMENTS]
<p>Dialga’s biggest issues with the this  set can all be in fact  resolved, but with varying degrees of  difficulty. Blissey becomes the  biggest counter to this set, since  Dialga lacks any way of KOing Blissey  reliably unless Blissey is under a  third of its health. Because Dialga  is great for knocking down the  physical walls of Ubers, it appreciates  physical attackers as its  teammates. Swords Dance Garchomp appreciates enjoys (appreciates is used already)   Groudon and Lugia being cleared out of the way, and doesn’t falter to   Thunder Wave from Blissey. Granted, Garchomp still has to fear Ice  Beam,  but Blissey oftentimes opts to use Seismic Toss to better handle   Dialga, Kyogre, and Palkia. Swords Dance Garchomp with a Haban Berry is   sufficient for the job, though Choice Band climbs in effectiveness   thanks to many of the Levitating  Pokemon being shut down by Draco Meteor  or Thunder. Once again, weather  is fairly important for this set to  work effectively. Much like the  Choice Scarf set, beware of Wobbuffet;  it poses less of a threat since  it is 2HKOed by Dragon Pulse, but it  still only takes 40% max from -2  SpA Draco Meteor. (Are you impressed  with Draco  Meteor's damage output against Wobbuffet or underwhelmed?  This should  be clearer in the writing.) (silly CM)</p>
[SET]
name: Choice Band
move 1: Outrage
move 2: Earthquake
move 3: Dragon Claw
move 4: Overheat / Stone Edge
items: Choice Band
nature: Adamant
EVs: 224 HP / 252 Atk / 32 Spe
[SET COMMENTS]
<p>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 to give a 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.</p>
<p>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.</p>
[ADDITIONAL COMMENTS]
<p>Choice Band Dialga has the exact opposite problems that Choice  Specs has. Outrage is a powerful attack, but it has the nasty drawback  in that it  prevents Dialga from switching out from a troublesome  position. Dialga  trades being able to handle Heatran and Ho-Oh (unless  it has Stone  Edge) for having issues with Lugia, Impish Groudon, and  Skarmory  (unless it has Overheat). While Lucario can’t take much of a  beating,  it can switch into Stone Edge and freely set up Swords Dance  followed  by a quickly KOing Dialga with Close Combat. Powerful special attackers and / or mixed attackers are recommended for this reason. Mixed Rayquaza  can outspeed and  annihilate most of these Pokemon when they switch in, outspeeding  most of them, barring Lugia (Lugia takes around 50% from Draco Meteor so it's still good to go).  Mewtwo is pretty effective here since Taunt  completely shuts down  Lugia and Skarmory, allowing Mewtwo to set up  Calm Mind freely. Mewtwo’s Its  only fear is Blissey that carry Seismic Toss,  which Dialga can at  least handle to an extent. As a partner, Wobbuffet  can set up Encore +  Tickle, then follow up with a Pokemon that knows  Pursuit to kill off  the opposing physical wall. Beware that Impish  Groudon sometimes carry  Toxic, which will harm the Wobbuffet's effectiveness of  Wobbuffet.</p>
[Team Options]
<p>Like most Pokemon, offensive Dialga enjoys the support of  Stealth Rock support, since it allows Dialga to turns certain 2HKOs into OHKOs, as  explained in several of the sets. Despite having an excellent typing,  wonderful defenses, (comma)  and an immunity to Toxic Spikes, Dialga unfortunately  lacks a reliable  way to restore its health beyond using Rest. Thus,  Wish support can  greatly extend its life span. The main Wish users are  Blissey, Jirachi,  and Latias. Latias is a particularly good user of Wish  for Dialga  because it resists Fighting and is immune to Ground moves,  while Dialga  resists Latias's Ghost and Dark weaknesses. Offensive  Dialga also  enjoy paralysis support (except for the Choice Scarf set,  where it's  redundant), because Dialga is slow by Uber standards.  Blissey, Jirachi,  and Latias can also use Thunder Wave (or in Jirachi's  case, Body Slam  with Serene Grace) to further support Dialga. Groudon is  another  excellent user of Thunder Wave because not only can it scare  off  Steel-types, but it can also lure in and paralyze Lugia, meaning  Lugia  will have a harder time using Roost to stall offensive   Dialga.</p>
<p>There are no Pokemon who that are guaranteed an easy switch-in on  Dialga, due to both its high offensive stats and versatility. Most Pokemon who that can stop Dialga require powerful super effective attacks, high  Speed, or good defenses. Even then, most of these problematic Pokemon cannot  switch in safely; they need to go for the revenge kill. Groudon in  particular can use a specially-defensive  EV spread to survive most of  Dialga's assaults, bar Choice Band  Outrages and Choice Specs Draco  Meteors, and use its STAB Earthquakes  to take Dialga down. Groudon It  may  also be able to set up Rock Polish to threaten a sweep if it  switches  into the right attack (such as Stone Edge or Thunder). A  Shaymin-S  carrying a Choice Scarf can solve this problem, thanks to  its immunity  to Earthquake, and its ability to outspeed and OHKO a Rock Polish  Groudon with Seed Flare. Life Orb Lucario and Life Orb Garchomp can OHKO  Dialga with Close Combat and Earthquake, (comma) respectively. Gengar can use  Focus Blast to OHKO Lucario, and Hidden Power Ice to OHKO Garchomp.  Although these Pokemon  cannot always OHKO the bulkier Dialga variants,  Gengar and Darkrai can  threaten to do a huge amount of damage to Dialga  with Focus Blast,  while Mewtwo can use the more accurate Aura Sphere. A  Mewtwo of your own Using your own Mewtwo can help since it (trying to avoid "a" pokemon) can switch into Gengar's Focus Blast and threaten to  OHKO it with Shadow Ball. A  Choice Scarf Heracross can switch into both  Darkrai's Focus Blast and  Mewtwo's Aura Sphere, and threaten to OHKO  them with Megahorn.  Heracross can also use Sleep Talk to strike back if  Darkrai uses Dark  Void.</p>
<p>Dialga is an extremely sturdy Pokemon who that is only hindered by  its weaknesses to Fighting and Ground attacks, thus Pokemon  who that  cover  those two weaknesses complement Dialga very well defensively.  Giratina-O  and Gengar are fantastic examples of this, as they are  immune to both  of Dialga's weaknesses, while they will both attract  Ghost and Dark  attacks that Dialga can easily switch into. Lugia is a  particularly good  defensive partner, as it not only sports an immunity  to Ground attacks,  but also a 4x resistance to Fighting attacks. Additionally, Latias, Latios, Rayquaza,  and Shaymin-S also  complement Dialga well, thanks to their immunities  to Ground moves and  resistances to Fighting moves. Although Skarmory is  only covering  Dialga's Ground weakness, it has the bonus of being able  to set up  Spikes on Pokemon such as Groudon and  Garchomp. Finally, the  many Psychic-types of Ubers, such as Wobbuffet  and Mewtwo, are able to  competently cover Dialga's weakness to Fighting  attacks.</p>
[Optional Changes]
<p>Dialga has loads of other options that can work as potential  support moves. Roar can work alongside Dialga's excellent sturdiness. (already in AC)   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 needing  to resorting to Draco Meteor or Overheat, but is otherwise generally a  poor choice. Iron Tail is poor  should be avoided, because as already noted, Steel is a  poor offensive type, and its 75% accuracy leaves much to be  desired.</p>
<p>Magnet Rise can be a good option on some Dialga sets, as it can  foil Dialga's arch enemy, Groudon. If using 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.</p>
<p>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  or 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.</p>
<p>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.</p>
[Counters]
<p>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. The If rain  is present, necessitates 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 takes a hit in its Base  Power 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. Metagross It also  does well at countering the Choice Band set,  though beware of stepping  into either Earthquake or Overheat in the  sun.</p>
<p>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 sets (sets is implying multiple so not a specific 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, (comma)  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. Lugia 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. Wobbuffet It  has to beware of the Mixed set when Draco Meteor is at full power  though.</p>
<p>Since it Dialga is a slow Pokemon, you can use faster Pokemon to  revenge kill Dialga 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.</p>
(most of the "it" changes throughout the analysis is because you did "Pokemon this. Pokemon that." repetition.)