#0334 · Gen 3

Altaria (Mega) — Best counters

Weaknesses

	Pokémon	Fast move	Charged move	Weather	Score
1	Zacian (Crowned)	steelMetal Claw	fairyPlay Rough	Overcast · partial	10012.0
2	Metagross (Mega)	steelBullet Punch	steelMeteor MashELITE	Snow	9611.5
3	Gardevoir (Mega)	fairyCharm	fairyDazzling Gleam	Overcast	9511.4
4	Beedrill (Mega)	poisonPoison Jab	poisonSludge Bomb	Overcast	9311.2
5	Gengar (Mega)	ghostLickELITE	poisonSludge Bomb	Overcast · partial	9110.8
6	Kyurem (White)	iceIce Fang	iceBlizzard	Snow	9010.8
7	Eternatus	poisonPoison Jab	poisonSludge Bomb	Overcast	8610.2
8	Metagross	steelBullet Punch	steelMeteor MashELITE	Snow	839.9
9	Enamorus (Incarnate)	fairyFairy Wind	fairyDazzling Gleam	Overcast	829.8
10	Alakazam (Mega)	psychicPsycho Cut	fairyDazzling GleamELITE	Overcast · partial	819.7
11	Naganadel	poisonPoison Jab	poisonSludge Bomb	Overcast	819.7
12	Lucario (Mega)	steelBullet Punch	steelFlash Cannon	Snow	809.5
13	Kyurem	steelSteel Wing	iceGlaciateELITE	Snow	799.5
14	Eternatus (Eternamax)	poisonPoison Jab	poisonSludge Bomb	Overcast	779.2
15	Nihilego	poisonPoison Jab	poisonSludge Bomb	Overcast	779.2
16	Diancie (Mega)	rockRock Throw	fairyMoonblast	Overcast · partial	769.1
17	Dialga	steelMetal Claw	steelIron Head	Snow	769.1
18	Deoxys (Attack)	poisonPoison Jab	electricZap Cannon	Rainy · partial	759.0
19	Roserade	poisonPoison Jab	poisonSludge Bomb	Overcast	758.9
20	Dialga (Origin)	steelMetal Claw	steelIron Head	Snow	748.9

Altaria (Mega) is weak to Poison (×1.6), Steel (×1.6), Ice (×1.6), Fairy (×1.6).
Watch its Flying/Dragon/Fairy/Fire moves — counters like Zacian (Crowned) and Metagross (Mega) take super-effective damage from them.
Overcast weather boosts Fairy moves ×1.2 — the best time to battle Altaria (Mega).

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