Project Victim of the Week

[Aragorn the King]

Week 109 Results:

Checks: Mega Charizard Y (SP458) | Mega Pidgeot (FireMonkeyGamer) | ScarfTran (nameless90)
Counters: Sap Sipper Azumarill (Hot dog pizza) | AV Tornadus-T (Infernal) | Mega Venusaur (GnralLao)

Thanks for all the votes guys! Also, thanks for the 500k views! :D

Week 110: Max Attack Mega Diancie


Diancie-Mega @ Diancite
Ability: Magic Bounce
EVs: 252 Atk / 4 SpA / 252 Spe
Naive Nature
- Moonblast
- Diamond Storm
- Hidden Power [Fire]
- Protect​

 

[HailFall]

Skarm as a counter (will add IMG when I get the chance)

Skarmory @ Leftovers / Shed Shell
Ability: Sturdy
EVs: 248 HP / 252 SpD / 8 Spe
Careful Nature
- Iron Head
- Roost
- Whirlwind / Taunt
- Spikes

Skarm eats any hit mega diancie can dish out and then OHKOes it with Iron Head.

4 SpA Mega Diancie Hidden Power Fire vs. 252 HP / 252+ SpD Skarmory: 118-140 (35.3 - 41.9%) -- 86.5% chance to 3HKO after Leftovers recovery

AraEDIT This calc makes me iffy to call it a counter: 252 Atk Mega Diancie Diamond Storm vs. 252 HP / 4 Def Skarmory: 144-169 (43.1 - 50.5%) -- 47.7% chance to 2HKO after Stealth Rock and Leftovers recovery

 

[heritage]

Counter

electric_forest (Suicune) @ Leftovers
Ability: Pressure
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Scald
- Rest
- Sleep Talk
- Calm Mind

Since this Mega Diancie doesn't have enough Special Attack investment, it isn't able to break past Suicune with Moonblast or Diamond Storm (Suicune's physical defense has more investment, making Diamond Storm pretty weak), even with Stealth Rock damage. From there, Suicune is able to PP stall Mega Diancie's attacks thanks to Pressure or set up with Calm Mind, preventing Mega Diancie from doing anything to it without some crazy critical hits. Scald easily 2HKOs in return, even if Suicune hasn't boosted up yet, and it can Rest off damage taken.

0 SpA Mega Diancie Moonblast vs. 252 HP / 4 SpD Suicune: 136-162 (33.6 - 40%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
252 Atk Mega Diancie Diamond Storm vs. 252 HP / 252+ Def Suicune: 126-148 (31.1 - 36.6%) -- 72.5% chance to 3HKO after Stealth Rock and Leftovers recovery

0 SpA Suicune Scald vs. 0 HP / 0- SpD Mega Diancie: 164-194 (68 - 80.4%) -- guaranteed 2HKO

 

[Infernal]

Jirachi @ Leftovers
Ability: Serene Grace
EVs: 240 HP / 236 SpD / 32 Spe
Careful Nature
- Stealth Rock
- Iron Head
- U-turn
- Healing Wish

Moonblast vs. Jirachi: 13.9 - 16.4%
Diamond Storm vs. Jirachi: 23.9 - 28.1% - Possible 5HKO
HP Fire vs. Jirachi: 23.9 - 28.4% - Possible 5HKO

This is a counter and handles Mega Diancie very well, as the calcs show. Jirachi is able to come in on any move Mega Diancie can use, and proceed to Iron Head for a kill or U-turn on a predicted to switch to grab some momentum. Because of its good bulk and various resistances to keep itself around for a while, Jirachi is able to perform this role consistently too. Jirachi's ability to handle Mega Diancie and other threats like Mega Gardevoir and Latios is a reason it's such a popular glue on the bulky offensive archetypes seen everywhere nowadays. Add the ability to use SR and Healing Wish to the mix and Jirachi's ability to compress so many roles becomes invaluable for these teams. The sample team with Mega Medicham here is an example of how Jirachi helps these archetypes keep Mega Diancie and company in check. Overall, Jirachi is a really nice answer to our victim, Mega Diancie, and a really common/effective choice to use as a Fairy check in general.

 

[InvisibleWater]

Counter

Empoleon @ Leftovers
Ability: Torrent
EVs: 248 HP / 8 Def / 252 SpD
Calm Nature
- Scald
- Roar
- Toxic / Stealth Rock
- Defog / Stealth Rock

Empoleon resists both of Diancie's STABs and takes little damage from HP Fire, allowing it to switch in on anything and take it out with Scald.

However, Scald is only capable of 2HKOing unless Torrent has been activated or hazards are up.

Calcs

Offensive:
0 SpA Empoleon Scald vs. 0 HP / 0- SpD Mega Diancie: 194-230 (80.4 - 95.4%) -- guaranteed 2HKO
0 SpA Torrent Empoleon Scald vs. 0 HP / 0- SpD Mega Diancie: 290-344 (120.3 - 142.7%) -- guaranteed OHKO

Defensive:
4 SpA Mega Diancie Moonblast vs. 248 HP / 252+ SpD Empoleon: 55-66 (14.8 - 17.7%) -- possible 9HKO after Leftovers recovery
252 Atk Mega Diancie Diamond Storm vs. 248 HP / 8 Def Empoleon: 105-124 (28.3 - 33.4%) -- 94.3% chance to 4HKO after Leftovers recovery
4 SpA Mega Diancie Hidden Power Fire vs. 248 HP / 252+ SpD Empoleon: 47-56 (12.6 - 15%) -- possibly the worst move ever

 

[SP458]

Serperior @ Leftovers
Ability: Contrary
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Leaf Storm
- Dragon Pulse
- Hidden Power [Fire]
- Glare

Status: check
The victim of the previous week happens to check Mega Diancie. It can't reliably switch in (all moves 2HKO after Rocks), but it outspeeds the princess of diamonds and OHKOes with Leaf Storm, even when it's in base forme.

Calcs

Against Serperior:
4 SpA Mega Diancie Moonblast vs. 0 HP / 4 SpD Serperior: 160-190 (54.9 - 65.2%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Mega Diancie Diamond Storm vs. 0 HP / 0 Def Serperior: 199-235 (68.3 - 80.7%) -- guaranteed 2HKO after Leftovers recovery

Against Diancie:
252 SpA Serperior Leaf Storm vs. 0 HP / 0- SpD Mega Diancie: 306-360 (126.9 - 149.3%) -- guaranteed OHKO
252 SpA Serperior Leaf Storm vs. 0 HP / 0- SpD Diancie: 234-276 (97 - 114.5%) -- 75% chance to OHKO

 

[Sobi]

counter:

Venusaur @ Venusaurite
Ability: Chlorophyll
EVs: 248 HP / 96 Def / 144 SpD / 20 Spe
Bold Nature
- Giga Drain
- Sludge Bomb
- Synthesis
- Hidden Power Fire

mega venusaur can take 1 or 2 diamond storm's from mega diancie and respond with a giga drain, which 2HKOes diancie. resists mega diancie's main STAB move, moonblast, and takes pitiful damage from HP Fire thanks to its typing.

0 SpA Mega Venusaur Giga Drain vs. 0 HP / 0- SpD Mega Diancie: 198-234 (82.1 - 97%) -- guaranteed 2HKO

252 Atk Mega Diancie Diamond Storm vs. 248 HP / 96+ Def Mega Venusaur: 135-159 (37.1 - 43.8%) -- guaranteed 3HKO

 

[Random Passerby]

Name: Metagross
Status: Check

Metagross @ Metagrossite
Ability: Clear Body
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Meteor Mash
- Thunder Punch
- Ice Punch
- Bullet Punch

With an imperfect Speed IV, Mega Diancie is outsped by Mega Metagross who OHKOes it with Meteor Mash. Bullet Punch is used just in case Metagross hasn't Mega Evolved yet. Mega Metagross also avoids the 2HKO from any of Mega Diancie's attacks if Stealth Rock isn't up (if it is, HP Fire has a 0.4% chance to 2HKO which won't happen as Mega Metagross outspeeds Mega Diancie).

Calculations with Mega Metagross

0 SpA Mega Diancie Hidden Power Fire vs. 0 HP / 0 SpD Mega Metagross: 120-142 (39.8 - 47.1%) -- 0.4% chance to 2HKO after Stealth Rock
0 SpA Mega Diancie Moonblast vs. 0 HP / 0 SpD Mega Metagross: 71-84 (23.5 - 27.9%) -- guaranteed 4HKO after Stealth Rock
252 Atk Mega Diancie Diamond Storm vs. 0 HP / 4 Def Mega Metagross: 67-79 (22.2 - 26.2%) -- 88.7% chance to 4HKO after Stealth Rock
252 Atk Tough Claws Mega Metagross Meteor Mash vs. 0 HP / 0 Def Mega Diancie: 784-928 (325.3 - 385%) -- guaranteed OHKO
252 Atk Tough Claws Mega Metagross Bullet Punch vs. 0 HP / 0 Def Mega Diancie: 348-412 (144.3 - 170.9%) -- guaranteed OHKO

Calculations with unevolved Metagross

0 SpA Mega Diancie Hidden Power Fire vs. 0 HP / 0 SpD Metagross: 142-168 (47.1 - 55.8%) -- guaranteed 2HKO after Stealth Rock
0 SpA Mega Diancie Moonblast vs. 0 HP / 0 SpD Metagross: 84-99 (27.9 - 32.8%) -- 16.6% chance to 3HKO after Stealth Rock
252 Atk Mega Diancie Diamond Storm vs. 0 HP / 4 Def Metagross: 76-90 (25.2 - 29.9%) -- guaranteed 4HKO after Stealth Rock

 

[blank]

Bronzong @ Leftovers
Ability: Levitate
EVs: 252 HP / 4 Def / 252 SpD
Sassy Nature
- Gyro Ball
- Earthquake
- Hidden Power [Ice]
- Stealth Rock

spdef skarmory and jirachi were taken; bronzong does the same thing as them vs. diancie, but it doesn't fit on as many teams due to it being a worse version of them basically. regardless, it works for this project since it's a nice counter to mega diancie in general. bronzong has nice bulk and resists both of diancie's stabs, and hidden power fire doesn't really do much thanks to bronzong's great spdef :p. furthermore, bronzong has levitate, meaning earth power isn't a problem if your opponent is running that. this is pretty self explanatory lol :3c.

while the comparison to other steels is pretty clear, bronzong is the best check in a vacuum. jirachi and mega metagross take quite a bit of damage from earth power (especially mega metagross), mega scizor takes a lot of damage from hidden power fire, and max attack diancie diamond storm can deal up to 50% damage to specially defensive skarmory. i know that for this example diancie isn't running earth power, but it's still worth mentioning in general :p.

finally, bronzong is 10x cuter than every other check to mega diancie :DD

calcs

4 SpA Mega Diancie Moonblast vs. 252 HP / 252+ SpD Bronzong: 51-60 (15 - 17.7%) -- possible 9HKO after Leftovers recovery
252 Atk Mega Diancie Diamond Storm vs. 252 HP / 0 Def Bronzong: 84-99 (24.8 - 29.2%) -- possible 5HKO after Leftovers recovery
4 SpA Mega Diancie Hidden Power Fire vs. 252 HP / 252+ SpD Bronzong: 86-102 (25.4 - 30.1%) -- 0.1% chance to 4HKO after Leftovers recovery

compared to

252 Atk Mega Diancie Diamond Storm vs. 252 HP / 4 Def Skarmory: 144-169 (43.1 - 50.5%) -- guaranteed 3HKO after Leftovers recovery
4 SpA Mega Diancie Hidden Power Fire vs. 248 HP / 200 SpD Mega Scizor: 216-256 (62.9 - 74.6%) -- guaranteed 2HKO
4 SpA Mega Diancie Hidden Power Fire vs. 0 HP / 0 SpD Mega Scizor: 264-312 (93.9 - 111%) -- 56.3% chance to OHKO

not doing the earth power calcs since this example isn't running earth power :p

 

[Eclipse]

Gastrodon-East (the only Gastro) as a counter.

Gastrodon @ Leftovers
Ability: Storm Drain
EVs: 252 HP / 88 Def / 168 SpD
Sassy Nature
- Scald
- Earthquake
- Curse
- Recover

Curse Gastrodon acts as a counter to this specific Diancie variant, as Moonblast now does less damage and with my spread, Moonblast 4HKO's Gastro pretty much all the time, meaning Gastrodon can use Diancie as setup fodder to setup Curses while being able to take out Diancie with Scald/EQ (although its unboosted attacks can't OHKO Diancie back):

4 SpA Mega Diancie Moonblast vs. 252 HP / 168+ SpD Gastrodon: 136-162 (31.9 - 38%) -- 0.5% chance to 3HKO after Leftovers recovery

252 Atk Mega Diancie Diamond Storm vs. 252 HP / 88 Def Gastrodon: 115-136 (26.9 - 31.9%) -- 46.1% chance to 4HKO after Leftovers recovery

0 SpA Gastrodon Scald vs. 0 HP / 0- SpD Mega Diancie: 168-198 (69.7 - 82.1%) -- guaranteed 2HKO

0 Atk Gastrodon Earthquake vs. 0 HP / 0 Def Mega Diancie: 170-204 (70.5 - 84.6%) -- guaranteed 2HKO (+1 OHKO's however)

 

[HappyHoopa05]

Set

Infernape @ Leftovers
Ability: Blaze / Iron Fist
EVs: 248 HP / 88 Def / 124 SpD / 48 Spe
Jolly Nature
- Will-O-Wisp
- Slack Off
- Taunt
- Flare Blitz / Fire Punch

Defensive Infernape, as a Checker, can enter when Serperior is getting behind substitute and kill it with 2 Flare Blitz, while tanking two Leaf Storms, but if your opponent predict the switch, you may be in trouble, as your flare blitz has 50% chance of 1HKO, so Stealth Rock damage is needed if you want a safe kill. Fire punch can be used instead of Flare Blitz if Recoil damage is getting annoying, but i won't recommend it, as serperior 3HKO you with leaf storm (for this reason i don't consider him a counter).

AraEDIT: Last week was Serperior -- this week we're nomming checks and counters to Mega Diancie.

 

[Martin]

Counter

Nidoqueen (F) @ Life Orb
Ability: Sheer Force
EVs: 120 HP / 252 SpA / 136 Spe
Modest Nature
IVs: 0 Atk
- Stealth Rock
- Sludge Wave
- Earth Power
- Ice Beam

Nidoqueen makes for a nice counter to max attack Mega Diancie, taking jack-all from any of Diancie's attacks due to the lack of Earth Power and being able to OHKO back with Earth Power as well as having a 6.3% chance to OHKO with Sludge Wave, meaning that it doesn't need to predict too heavily with with its STABs. The listed EV spread allows it to outpace adamant Tyranitar and everything slower than it, although a frailer spread of 48 HP / 252 SpA / 208 Spe can be run to outpace neutral base 70s, with it benefitting from the ability to take Focus Punch or Force Palm considerably better than Nidoking can when switching into Breloom and proceeding to be able to avoid being hit by Bullet Seed on the following turn. Basically this thrives on the added bulk allowing it to take on Mega Diancie repeatedly throughout the match at the cost of speed, as modest Nidoqueen hits about as hard as timid Nidoking does, with it having four more points in SpA than the latter.

 

[Random Passerby]

Set

Infernape @ Leftovers
Ability: Blaze / Iron Fist
EVs: 248 HP / 88 Def / 124 SpD / 48 Spe
Jolly Nature
- Will-O-Wisp
- Slack Off
- Taunt
- Flare Blitz / Fire Punch

Defensive Infernape, as a Checker, can enter when Serperior is getting behind substitute and kill it with 2 Flare Blitz, while tanking two Leaf Storms, but if your opponent predict the switch, you may be in trouble, as your flare blitz has 50% chance of 1HKO, so Stealth Rock damage is needed if you want a safe kill. Fire punch can be used instead of Flare Blitz if Recoil damage is getting annoying, but i won't recommend it, as serperior 3HKO you with leaf storm (for this reason i don't consider him a counter).

The current victim is Mega Diancie

 

[michaeloche]

Been a while for me.

Scizor @ Scizorite
Ability: Light Metal -> Technician
EVs: 248 HP / 44 Atk / 16 Def / 200 Spe
Impish Nature
- Bullet Punch
- Roost
- Swords Dance
- Knock Off

Role: Soft Counter

Bulky SD Mega Scizor laughs at Moonblast, requires two max rolls to be 2HKOed by Diamond Storm with rocks up, and, assuming it has mega evolved, can even survive HP Fire after rocks and one layer of Spikes. I don't think I need to tell you what Bullet Punch does in return, but I'm including it in the calcs anyway.

calcs

4 SpA Mega Diancie Moonblast vs. 248 HP / 200 SpD Mega Scizor: 63-75 (18.3 - 21.8%) -- possible 5HKO
252 Atk Mega Diancie Diamond Storm vs. 248 HP / 16+ Def Mega Scizor: 127-151 (37 - 44%) -- guaranteed 3HKO (0.4% chance to 2HKO after Stealth Rock)
4 SpA Mega Diancie Hidden Power Fire vs. 248 HP / 200 SpD Mega Scizor: 216-256 (62.9 - 74.6%) -- guaranteed 2HKO after Stealth Rock and 1 layer of Spikes

44 Atk Technician Mega Scizor Bullet Punch vs. 0 HP / 0 Def Mega Diancie: 352-420 (146 - 174.2%) -- guaranteed OHKO

 

[detviech]

Bulky Excadrill as a Counter

Excadrill @ Leftovers
Ability: Mold Breaker
EVs: 252 HP / 4 Atk / 252 SpD
Careful Nature
- Earthquake
- Iron Head
- Rapid Spin
- Stealth Rock

Bulky Drill likes the fact, that this is a physical Diancie. Diancies strongest move, Diamond Storm, is four times resisted, Moonblast is also not very effective, and HP-Fire isn't very strong without investment. Drill can even get Rocks up, if it wants to because of Mold Breaker, ignoring the fact, that it has Magic Bounce.
The only drawback is, that it doesn't have reliable Recovery besides Lefties. But this problem can be solved with something like Wish Support. Of course Drill OHKOs Diancie with its STAB moves all the time.

Calcs

252 Atk Mega Diancie Diamond Storm vs. 252 HP / 0 Def Excadrill: 72-85 (16.9 - 20%) -- possible 7HKO after Leftovers recovery

4 SpA Mega Diancie Moonblast vs. 252 HP / 252+ SpD Excadrill: 72-86 (16.9 - 20.2%) -- possible 7HKO after Leftovers recovery

4 SpA Mega Diancie Hidden Power Fire vs. 252 HP / 252+ SpD Excadrill: 124-146 (29.2 - 34.4%) -- 99.8% chance to 4HKO after Leftovers recovery

4 Atk Mold Breaker Excadrill Earthquake vs. 0 HP / 0 Def Mega Diancie: 258-306 (107 - 126.9%) -- guaranteed OHKO

4 Atk Mold Breaker Excadrill Iron Head vs. 0 HP / 0 Def Mega Diancie: 412-492 (170.9 - 204.1%) -- guaranteed OHKO

 

[nameless90]

Counter: AV Metagross

Metagross @ Assault Vest
Ability: Clear Body
EVs: 252 HP / 160 Atk / 96 SpD
Adamant Nature
- Pursuit
- Meteor Mash
- Bullet Punch
- Earthquake

160+ Atk Metagross Bullet Punch vs. 0 HP / 0 Def Mega Diancie: 256-304 (106.2 - 126.1%) -- guaranteed OHKO
4 SpA Mega Diancie Hidden Power Fire vs. 252 HP / 96 SpD Assault Vest Metagross: 86-102 (23.6 - 28%) -- 83.3% chance to 4HKO

Regular Metagross resists Rock attacks and is enough bulky to stomach 3 Ground hits on the special side.
A priority Bullet Punch is enough to OHKO Mega Diancie and the ability Clear Body ensures this KO even with Intimidate users around.

 

[FMG]

Check: Choice Banded Azumarill

Banded Azumarill is a good CHECK to Mega Diancie. Aqua Jet has a decent chance of killing M-Diancie from full. Also Azumarill can take any one hit from Diancie. Also Play Rough and Waterfall can 100% Diancie from full.

Calcs

252+ Atk Choice Band Huge Power Azumarill Aqua Jet vs. 0 HP / 0 Def Mega Diancie: 218-260 (90.4 - 107.8%) -- 43.8% chance to OHKO

252+ Atk Choice Band Huge Power Azumarill Play Rough vs. 0 HP / 0 Def Mega Diancie: 247-292 (102.4 - 121.1%) -- guaranteed OHKO

252 Atk Mega Diancie Diamond Storm vs. 172 HP / 0 Def Azumarill: 229-271 (59.6 - 70.5%) -- guaranteed 2HKO

4 SpA Mega Diancie Moonblast vs. 172 HP / 0 SpD Azumarill: 186-220 (48.4 - 57.2%) -- 93.4% chance to 2HKO
Do I really need to calc waterfall damage. LOL

 

[Raymond Quaza]

Landorus-Therian @ Choice Scarf
Ability: Intimidate
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Earthquake
- Stone Edge
- Knock Off
- U-turn

Scarfed Landorus-T as a Check. Scarfed Landorus is able to outspeed and OHKO Mega Diancie without any trouble via STAB Earthquake. Even if there was a circumstance where Mega Diancie outsped Landorus-T, Mega Diancie can only 2HKO him at best, allowing Landorus-T to win overall.

Calcs:
4 SpA Mega Diancie Moonblast vs. 0 HP / 0 SpD Landorus-T: 186-220 (58.3 - 68.9%) -- guaranteed 2HKO after Stealth Rock
-1 252 Atk Mega Diancie Diamond Storm vs. 0 HP / 4 Def Landorus-T: 139-165 (43.5 - 51.7%) -- 99.6% chance to 2HKO after Stealth Rock

252 Atk Landorus-T Earthquake vs. 0 HP / 0 Def Mega Diancie: 326-386 (135.2 - 160.1%) -- guaranteed OHKO

 

[HappyHoopa05]

Scarf Magnezone as a Counter

Magnezone @ Choice Scarf
Ability: Magnet Pull
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Volt Switch
- Hidden Power [Fire]
- Flash Cannon
- Thunderbolt

Magnezone can easily get in Diamond Storm / Moon Blast / Protect and kill with Flash Cannon, as it outspeeds Diancie with with Choice Scarf. Hidden Power Fire is 2HKO.

Calcs

Magnezone:
252 SpA Magnezone Flash Cannon vs. 0 HP / 0- SpD Mega Diancie: 540-636 (224 - 263.9%) -- guaranteed OHKO

Diancie:
252 Atk Mega Diancie Diamond Storm vs. 0 HP / 4 Def Magnezone: 84-99 (29.8 - 35.2%) -- 23.6% chance to 3HKO

4 SpA Mega Diancie Moonblast vs. 0 HP / 0 SpD Magnezone: 84-99 (29.8 - 35.2%) -- 23.6% chance to 3HKO

4 SpA Mega Diancie Hidden Power Fire vs. 0 HP / 0 SpD Magnezone: 144-170 (51.2 - 60.4%) -- guaranteed 2HKO.

 

[Lemon Ginger]

Mega Aggron shows up in Diancie's nightmares as a counter

Aggron-Mega @ Aggronite
Ability: Filter
EVs: 248 HP / 8 Atk / 252 SpD
Careful Nature
- Curse
- Heavy Slam
- Rest
- Sleep Talk

0 SpA Mega Diancie Hidden Power Fire vs. 252 HP / 252+ SpD Filter Mega Aggron: 82-97 (23.8 - 28.1%) -- 91.8% chance to 4HKO
0 SpA Mega Diancie Earth Power vs. 252 HP / 252+ SpD Filter Mega Aggron: 121-144 (35.1 - 41.8%) -- guaranteed 3HKO

Heavy slam blows Diancie away.

Aggron can switch in twice, doesn't give a crap about physically inclined Diancie, can set up itself (unless Diancie has E-Power). Even max investment (non-modest) can't 2HKO:

252 SpA Mega Diancie Earth Power vs. 252 HP / 252+ SpD Filter Mega Aggron: 144-169 (41.8 - 49.1%) -- guaranteed 3HKO

Overall one of the safest switches into Mega-Diancie.


P.S. Someone do rest talk mega swampert

 

[jordanthejq12]

Doublade as a soft counter.

Doublade @ Eviolite
Ability: No Guard
EVs: 248 HP/8 Def/252 SpD
Sassy Nature
- Gyro Ball
- Rest
- Toxic
- Shadow Sneak

We're running out of Steels, aren't we? Anyway, Doublade can (though it probably shouldn't) switch into anything, taking 34.8 - 41.7% from HP Fire (requiring rocks and 1 spike to even consider a 2HKO) and then wiping it out with Gyro Ball.

 

[ericaroselia]

Reserve mega Aggron

P.S. Someone do rest talk mega swampert

Swampert-Mega @ Swampertite
Ability: Damp
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Curse
- Rest
- Sleep Talk
- Waterfall

Mega Swampert is a counter to Mega Diancie since it resists Diamond Storm and laughs at Moonblast due to its high spD and Diancie's lack of spA and can always beat with Waterfall.

0 SpA Mega Diancie Moonblast vs. 252 HP / 252+ SpD Mega Swampert: 105-124 (25.9 - 30.6%) -- guaranteed 4HKO

252 Atk Mega Diancie Diamond Storm vs. 252 HP / 4 Def Mega Swampert: 87-103 (21.5 - 25.4%) -- 0.6% chance to 4HKO

0 Atk Mega Swampert Waterfall vs. 0 HP / 0 Def Mega Diancie: 228-270 (94.6 - 112%) -- 68.8% chance to OHKO

 

[DoABarrelRoll]

keldeo @ choice scarf
ability: justified
evs: 4 hp / 252 spa / 252 spe
timid nature

- scald
- hydro miss
- secret sword
- hp fire

switches into anything but moonblast and proceeds to beat up mega diancie with scald. CHECK

 

[Icing On Da Cake]

Submitting NidoKING as a Check

Since this particular Mega Diancie lacks Earth Power, NidoKING is able to avoid the 2HKO from any attack and proceed to blow Mega Diancie away. However, Mega Diancie has the ability to 2HKO if SR + at least 1 Spike is up, so NidoKING is only labeled as a check.

Relevant Calcs

Mega Diancie vs Nidoking w/o Hazard Damage

252 Atk Mega Diancie Diamond Storm vs. 0 HP / 0 Def Nidoking: 118-140 (38.9 - 46.2%) -- guaranteed 3HKO
4 SpA Mega Diancie Moonblast vs. 0 HP / 4 SpD Nidoking: 97-115 (32 - 37.9%) -- 95.5% chance to 3HKO
4 SpA Mega Diancie Hidden Power Fire vs. 0 HP / 4 SpD Nidoking: 83-98 (27.3 - 32.3%) -- guaranteed 4HKO

Mega Diancie vs Nidoking w/ Hazard Damage

252 Atk Mega Diancie Diamond Storm vs. 0 HP / 0 Def Nidoking: 118-140 (38.9 - 46.2%) -- 85.2% chance to 2HKO after Stealth Rock and 1 layer of Spikes (only needed 1 Spike)
4 SpA Mega Diancie Moonblast vs. 0 HP / 4 SpD Nidoking: 97-115 (32 - 37.9%) -- 63.3% chance to 2HKO after Stealth Rock and 3 layers of Spikes (needed all 3 spikes)
HP Fire is never a 2HKO from full, even with all hazards up.

NidoKING vs Mega Diancie

252 SpA Life Orb Sheer Force Nidoking Earth Power vs. 0 HP / 0- SpD Mega Diancie: 382-452 (158.5 - 187.5%) -- guaranteed OHKO
ded

 

[Aragorn the King]

Checks:

III Scarf Landorus-T
II Mega Metagross
II Mega Scizor

II Specially Defensive Skarmory
II Serperior

Metagross
I CB Azumarill
Scarf Keldeo
Scarf Magezone
Nidoking


Counters:

X Jirachi
III Gastrodon
III Defensive Mega Venusaur

II AV Metagross
II Suicune
Empoleon
II Bronzong
Nidoqueen
Bulky Excadrill
II AV Tangrowth
I Doublade
Mega Swampert

You may vote for one check and two counters.

My tie-breaker: Meta Metagross and Mega Scizor
​