What it does on the ladder
Gyarados appears on 0.30% of Regulation M-B teams, which
is 122nd of the 282 Pokémon with enough games to measure.
The move it almost always carries is Waterfall, on 90.9% of sets.
The item is usually Sitrus Berry at 47.4%.
The ability is split: Intimidate on 97.3% and Moxie on 2.7%.
Those are Smogon's published usage figures, not anything measured here, and they describe what
the ladder plays rather than what is strongest. The full set is in the panel above.
The Pokémon itself
Gyarados is number 130 in the National Dex, a Kanto Pokémon, Water and Flying
with a base stat total of 540 — 20th of the 234 Pokémon
legal in this regulation. Its best stat is Attack at 125, 23rd
in the format; its weakest is Sp. Atk at 60, 172nd.
It can have Intimidate and Moxie.
The Champions module tiers it UU.
It sits in a 2-stage line: Magikarp → Gyarados.
Not all of that line is legal in this regulation — Magikarp is not.
What gets through
As Water and Flying, 2 of the eighteen attacking types do extra damage to it, and Electric lands for quadruple. It
resists 5 and is immune to 1. The board above
has all of it. One other legal Pokémon shares the same typing and the same board: Pelipper.
What threatens it
Smogon publishes no head-to-head checks-and-counters data for doubles formats, so this list is
computed, not measured: the most-played Regulation M-B Pokémon carrying a damaging
move of a type Gyarados takes extra damage from.
- Garchomp — Rock Slide (Rock, ×2), on 75.9% of its sets
- Farigiraf — Thunderbolt (Electric, ×4), on 59.2% of its sets
- Archaludon — Electro Shot (Electric, ×4), on 98.6% of its sets
- Aerodactyl-Mega — Rock Slide (Rock, ×2), on 99.8% of its sets
- Raichu-Mega-Y — Zap Cannon (Electric, ×4), on 98.8% of its sets
- Mawile-Mega — Rock Slide (Rock, ×2), on 35.4% of its sets
Speed and weight
At level 50 with a boosting nature and full investment, Gyarados reaches
146 Speed; left uninvested with a neutral nature it sits at
101. Invested, it outruns 10 of the 20
most-used Pokémon in the regulation when they are invested too — which is the comparison that
decides who moves first.
It weighs 235 kg, so Grass Knot and Low Kick hit it for 120 base
power. That is a real consideration in a format where both are common.
Its move pool
Gyarados learns 102 moves in the Champions data.
66 of them do damage, across 13 of the eighteen
types, and 15 share a type with it and so get the same-type bonus.
Its hardest-hitting same-type move is Hurricane at 110 base power, though the biggest number in the pool is Giga Impact at 150.
It has no priority move, so it moves in Speed order every turn.
That pool is what the team builder reads from when you seat it, and the
damage calculator will take it as the attacker with
the form already chosen.