#0379 · Gen 3 · Legendary

Registeel — Best counters

Weaknesses

	Pokémon	Fast move	Charged move	Weather	Score
1	Lucario (Mega)	fightingForce PalmELITE	fightingAura Sphere	Overcast	10013.9
2	Blaziken (Mega)	fightingCounter	fireBlast BurnELITE	Clear · partial	9513.2
3	Charizard (Mega Y)	fireFire Spin	fireBlast BurnELITE	Clear	9212.8
4	Groudon (Primal)	groundMud Shot	groundPrecipice BladesELITE	Clear	9212.7
5	Blacephalon	fireIncinerate	fireOverheat	Clear	8411.7
6	Heracross (Mega)	fightingCounter	fightingClose Combat	Overcast	8311.5
7	Garchomp (Mega)	groundMud Shot	groundEarthquake	Clear	8111.3
8	Alakazam (Mega)	fightingCounterELITE	fightingFocus Blast	Overcast	8111.2
9	Reshiram	fireFire Fang	fireFusion FlareELITE	Clear	8011.2
10	Landorus (Therian)	groundMud Shot	groundSandsear StormELITE	Clear	7911.0
11	Charizard (Mega X)	fireFire Spin	fireBlast BurnELITE	Clear	7910.9
12	Pheromosa	fightingLow Kick	fightingFocus Blast	Overcast	7810.8
13	Lucario	fightingForce PalmELITE	fightingAura Sphere	Overcast	7610.6
14	Lopunny (Mega)	fightingDouble Kick	fightingFocus Blast	Overcast	7510.4
15	Chandelure	fireFire Spin	fireOverheat	Clear	7410.3
16	Houndoom (Mega)	fireFire Fang	fireFire Blast	Clear	7410.3
17	Gallade (Mega)	fightingLow Kick	fightingClose Combat	Overcast	7410.3
18	Volcarona	fireFire Spin	fireOverheat	Clear	7210.0
19	Terrakion	fightingDouble Kick	fightingSacred SwordELITE	Overcast	7210.0
20	Darmanitan (Standard)	fireFire Fang	fireOverheat	Clear	7210.0

Registeel is weak to Fighting (×1.6), Ground (×1.6), Fire (×1.6).
Watch its Steel/Fighting/Normal/Electric moves — counters like Lucario (Mega) and Charizard (Mega Y) take super-effective damage from them.
Overcast weather boosts Fighting moves ×1.2 — the best time to battle Registeel.

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