#0719 · Gen 6 · Mythical

Diancie (Mega) — Best counters

Weaknesses

steel×2.56 double weaknessground×1.60water×1.60grass×1.60

	Pokémon	Fast move	Charged move	Weather	Score
1	Metagross (Mega)	steelBullet Punch	steelMeteor MashELITE	Snow	10018.4
2	Metagross	steelBullet Punch	steelMeteor MashELITE	Snow	8615.8
3	Lucario (Mega)	steelBullet Punch	steelFlash Cannon	Snow	8315.2
4	Dialga	steelMetal Claw	steelIron Head	Snow	7914.5
5	Dialga (Origin)	steelMetal Claw	steelIron Head	Snow	7714.2
6	Genesect	steelMetal Claw	steelMagnet Bomb	Snow	7613.9
7	Aggron (Mega)	steelIron Tail	steelHeavy Slam	Snow	7313.5
8	Scizor (Mega)	steelBullet Punch	steelIron Head	Snow	7313.5
9	Excadrill	steelMetal Claw	steelIron Head	Snow	7313.4
10	Aerodactyl (Mega)	steelSteel Wing	steelIron Head	Snow	7113.1
11	Kyogre (Primal)	waterWaterfall	waterOrigin PulseELITE	Rainy	7012.9
12	Duraludon	steelMetal Claw	steelFlash Cannon	Snow	7012.9
13	Groudon (Primal)	groundMud Shot	groundPrecipice BladesELITE	Clear	6912.7
14	Zacian (Crowned)	steelMetal Claw	fightingClose Combat	Overcast · partial	6812.6
15	Kingambit	steelMetal Claw	steelIron Head	Snow	6812.5
16	Bisharp	steelMetal Claw	steelIron Head	Snow	6612.2
17	Sceptile (Mega)	grassBullet Seed	grassFrenzy PlantELITE	Clear	6612.1
18	Kyurem (White)	steelSteel Wing	iceBlizzard	Snow	6512.0
19	Melmetal	electricThunder Shock	steelDouble Iron BashELITE	Snow · partial	6411.8
20	Empoleon	steelSteel Wing	steelFlash Cannon	Snow	6411.7

Steel hits for ×2.56 — Diancie (Mega)'s Rock/Fairy typing is double-weak, so those attackers outperform their score gap.
Watch its Normal/Rock/Fairy moves — counters like Aerodactyl (Mega) and Sceptile (Mega) take super-effective damage from them.
Snow weather boosts Steel moves ×1.2 — the best time to battle Diancie (Mega).

Rankings are estimated cycle DPS (attack stat × move damage ÷ cycle time, with STAB and type effectiveness). Not a full battle simulation.