#0154 · Gen 2

Meganium (Mega) — Best counters

Weaknesses

poison×2.56 double weaknessflying×1.60steel×1.60fire×1.60ice×1.60

	Pokémon	Fast move	Charged move	Weather	Score
1	Beedrill (Mega)	poisonPoison Jab	poisonSludge Bomb	Overcast	10017.8
2	Eternatus	poisonPoison Jab	poisonSludge Bomb	Overcast	9216.4
3	Gengar (Mega)	ghostHex	poisonSludge Bomb	Overcast · partial	9016.1
4	Naganadel	poisonPoison Jab	poisonSludge Bomb	Overcast	8715.5
5	Eternatus (Eternamax)	poisonPoison Jab	poisonSludge Bomb	Overcast	8314.8
6	Nihilego	poisonPoison Jab	poisonSludge Bomb	Overcast	8214.7
7	Roserade	poisonPoison Jab	poisonSludge Bomb	Overcast	8014.3
8	Revavroom	poisonPoison Jab	poisonGunk Shot	Overcast	7513.4
9	Blaziken (Mega)	fireFire Spin	fireBlast BurnELITE	Clear	7413.2
10	Overqwil	poisonPoison Jab	poisonSludge Bomb	Overcast	7313.1
11	Deoxys (Attack)	poisonPoison Jab	electricZap Cannon	Rainy · partial	7313.0
12	Charizard (Mega Y)	fireFire Spin	fireBlast BurnELITE	Clear	7212.8
13	Toxicroak	poisonPoison Jab	poisonSludge Bomb	Overcast	7012.4
14	Rayquaza (Mega)	flyingAir Slash	flyingHurricaneELITE	Windy	6812.2
15	Salazzle	poisonPoison Jab	poisonSludge Wave	Overcast	6812.2
16	Gengar	ghostHex	poisonSludge Bomb	Overcast · partial	6712.0
17	Scolipede	poisonPoison Jab	poisonSludge Bomb	Overcast	6712.0
18	Victreebel	poisonAcid	poisonSludge Bomb	Overcast	6711.9
19	Blacephalon	fireIncinerate	fireOverheat	Clear	6611.7
20	Grafaiai	poisonPoison Jab	poisonSludge Bomb	Overcast	6611.7

Poison hits for ×2.56 — Meganium (Mega)'s Grass/Fairy typing is double-weak, so those attackers outperform their score gap.
Overcast weather boosts Poison moves ×1.2 — the best time to battle Meganium (Mega).

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