Gyarados is a massive threat whom one should be prepared for. A high base 125 Attack, an excellent offensive typing in Water, and a diverse movepool all make Gyarados a top-tier sweeper. Gyarados is also easy to switch in, and can even serve defensive roles, thanks to 95 / 79 / 100 base defensive stats, Intimidate, and key resistances to Water, Fighting, Bug, Fire, and Steel, plus an immunity to Ground. Gyarados isn't without its shortcomings though. Electric moves are rather common in the standard metagame, and Gyarados's 4x weakness to them means Gyarados can find it hard to deal with very fast or bulky Pokémon who pack electricity. Furthermore, Stealth Rock limits the times Gyarados can switch in. Combined with sandstorm and Life Orb recoil, Gyarados may end up dying more quickly than you want it to. Overall, with the right support, Gyarados can easily bulldoze its way through a weakened team, and is a valuable addition to any OU team.
Gyarados is a very potent sweeper, due to its powerful, diverse movepool, excellent stats and Intimidate. With an Adamant nature, Gyarados hits 391 Speed, outspeeding +Speed base 120s and Choice Scarf Tyranitar; however, with a Jolly nature, Gyarados gets the jump on Timid Jolteon, so that is worthy of consideration. Waterfall is Gyarados's main means of doing damage, being able to break through the majority of walls, since most don't resist Water. Stone Edge provides coverage with Waterfall, hitting Zapdos, Dragonite, and other Gyarados.
Earthquake lets Gyarados take out Empoleon, Magnezone, and Metagross, while providing good coverage with Gyarados's other attacks. Bounce is another good option for the last slot, being Gyarados's most powerful attack on the set, and more importantly, allowing Gyarados to get past some of its usual counters, such as defensive Starmie and Celebi. Ice Fang can be useful to hit Grass and Dragon-types, but Bounce can hit all of them harder with the exception of Gliscor, Dragonite, and Flygon.Team Options & Additional Comments >>>
This set sacrifices offensive power and Speed for the ability to use its typing and defenses to set up on the likes of Heatran, Infernape, Lucario, and Scizor. Stone Edge is the main option for a secondary attack, for heavily damaging other Gyarados, Dragonite, and Zapdos. Water / Rock is also only resisted by Breloom and Empoleon in OU. The combination of Waterfall and Bounce, however, is only resisted by Empoleon and Lanturn. It also has the merit of an extra turn of Leftovers recovery, and the 30% paralysis chance is extremely useful for most teams. Other options include Return and Earthquake. Return hits most Pokémon who resist Water for neutral damage, and the combo is only resisted by Empoleon and Shedinja. Earthquake can help Gyarados deal with Magnezone and Empoleon, but it leaves it at the mercy of set-up by Pokémon like Dragonite. Taunt allows Gyarados to have a better fighting chance against Skarmory and Celebi. Skarmory will be unable to Whirlwind Gyarados out, while Gyarados sets up on the helpless Skarmory. Celebi will be unable to paralyze Gyarados, and Bounce severely weakens it.Team Options & Additional Comments >>>
Good defenses combined with Intimidate and an excellent array of resistances means that Gyarados can take on a defensive role. Rest can cure Gyarados of any damage it has lost through direct attacks, Stealth Rock, and other residual damage, while Sleep Talk lets Gyarados perform moves while it's asleep. Rest also removes status, so Gyarados can take on Heatran and Dusknoir without being crippled. The large number of EVs in HP and Defense makes Gyarados an excellent check to some of the most common threats in OU, such as Lucario, Infernape and Heatran.
Waterfall is a very reliable STAB move for Gyarados to hurt Water-weak foes. Roar lets Gyarados shuffle the opponents. This is useful if you lack a phazer or you're using a stall team. Two other options are Stone Edge and Avalanche. Stone Edge provides nice coverage, hurting most Dragon-types and all Flying-types. Avalanche also does this, plus it also hurts Celebi.Team Options & Additional Comments >>>
Gyarados is perfectly capable of using a Choice Band to surprise some of its potential counters, despite not being as threatening as some of its other sets. Waterfall is incredibly powerful with a Choice Band boost, 2HKOing defensive Rotom-A after Stealth Rock. Payback is what Gyarados uses to beat many of its counters, 2HKOing Celebi after Stealth Rock and OHKOing Rotom-A and Starmie as they switch in. Stone Edge hits Flying-types that resist Water, such as other Gyarados and Dragonite. Earthquake prevents Empoleon, Magnezone, and Metagross from walling Gyarados, OHKOing Empoleon and Magnezone and 2HKOing Metagross. Ice Fang is an alternate option, hurting Breloom who would otherwise wall Gyarados, as well as being more accurate than Stone Edge as a move for hurting Flying types.Team Options & Additional Comments >>>
While RestTalk Roar Gyarados should only be used on stall teams with lots of entry hazards, this version plays nicely on any team looking for a solid mixed wall. Instead of Roaring out your opponents, this Gyarados threatens to set up against them and clean up their team. Forgoing Attack and investing in both defenses lets Gyarados set up against Pokemon who would otherwise be considered counters, such as Celebi, Empoleon, Swampert (without Roar), and Vaporeon (without Hidden Power Electric). It also excels at countering Fire-types (especially Heatran and any Infernape without Stone Edge) while still performing very well against the likes of Scizor and Lucario.
With a Careful nature, 96 Special Defense EVs ensure that a defensive Celebi's Grass Knot never inflicts more than 32%, meaning it will never 3HKO; Empoleon's Grass Knot is about equally powerful (Empoleon will rarely get a Petaya boost against this Gyarados), so these two will find themselves watching idly as Gyarados boosts its Attack and Speed. This also guarantees that Heatran's Fire Blast has only a very small chance to 3HKO after a Flash Fire (or Choice Specs) boost. 8 Speed is a minimal investment, but it is enough to outrun the neutral-natured base 100 Speed group after a single Dragon Dance, which can mean the difference between winning the game and being flinched to death by Jirachi; it also outspeeds Timid Rotom-A. The remainder goes into Defense to help Gyarados take physical attacks better, and this is amplified by Intimidate. This Gyarados laughs in the face of Breloom, as it does not fear Spore or any of Breloom's other attacks. Lastly, with all of these investments, this Gyarados will even be able to beat out powerful mixed attackers, including the big three Dragon-types of OU: Kingdra, Flygon, and Dragonite.Team Options & Additional Comments >>>
Wacan Berry can allow Gyarados to survive a Thunderbolt and get another Dragon Dance in. Lum Berry also grants Gyarados another boost, except it cures status. Choice Scarf can give Gyarados a boost in Speed, making it a good revenge killer.
Bite is Gyarados's best option against Slowbro. It also OHKOes Starmie after a Dragon Dance. Thunder Wave can cause problems with some of Gyarados's common switch-ins, working well with Waterfall, and Ground-types won't usually switch-in. Flail has good coverage with Waterfall and Substitute can get it to maximum power, but the high use of sandstorm makes this a difficult strategy. Gyarados has a great special movepool, with moves such as Hydro Pump, Fire Blast, Ice Beam, and Thunderbolt. Although Gyarados can 2HKO some physical walls, Gyarados's pitiful Special Attack makes a special Gyarados nothing more than a gimmick.
Dragon Dance Numbers
This section provides a useful reference to Gyarados's key "Dragon Dance Numbers", or precise EV investment needed to reach a certain Speed stat. This Speed stat is used to outrun a specific base Speed threat group. Notable opponents that should be taken into consideration include +Speed Starmie (maxing out at 361 Speed), +Speed Jolteon (maxing out at 394 Speed), and neutral Speed natured Choice Scarf Rotom-A (maxing out at 406 Speed).
Checks and Counters
Porygon2 with a defensive EV spread and Trace is the best counter to Gyarados. Thanks to Trace, Intimidate bounces back on Gyarados, and Porygon2 can unleash either Thunderbolt or Discharge to finish it off. Rotom-A can absorb a Waterfall, outpace most Gyarados, and retaliate with STAB Thunderbolt. Thunder Wave and Will-O-Wisp are also useful to cripple Gyarados. Timid Choice Scarf variants even outspeed +1 Jolly Gyarados and OHKO with Thunderbolt. Bold Cresselia can block most of Gyarados's attack for a while and use Charge Beam, while a combination of Thunder Wave and Reflect renders Gyarados without Taunt nearly useless.
Celebi's high HP and Defense lets it take on Ice Fang well, and can hit Gyarados hard with a 120 Base Power Grass Knot. Recover prevents it from being worn down so it can switch in repeatedly. An Impish Tangrowth can shrug off Ice Fangs with its 125 base Defense and use STAB Power Whip on Gyarados. Bounce does hurt them both badly though; 252 HP / 252 Def Bold Celebi, for example, is sometimes OHKOed by a +1 Life Orb Adamant Bounce with Stealth Rock support. Metagross with ThunderPunch stands a fair chance against Gyarados provided Gyarados isn't using Earthquake. Forretress can always Explode on Gyarados if need be as its high Defense lets it take a few beatings.
Water-types that carry Hidden Power Electric pose a bigger threat to Gyarados. Though they risk being 2HKOed sometimes by a Dragon Danced Stone Edge, they can attempt to stop the sweep: Milotic, Slowbro, Suicune, and Vaporeon are perfect examples of this. Starmie can revenge kill some forms of Gyarados, but it must tread lightly, as a Life Orbed Stone Edge can nearly OHKO it if Gyarados has a Dragon Dance under its belt, and a +1 Life Orb Bounce OHKOes 136 HP / 156 Def Timid Starmie most of the time with Stealth Rock support.
Skarmory has a chance to at least threaten Gyarados if it has Brave Bird. Due to the lack of Leftovers when running Shed Shell and the recoil from Brave Bird, this is a risky 3HKO to attempt, and bulky Gyarados can take some of the beating. Taunt prevents Skarmory from its usual strategies of using Roost and Whirlwind to counter Gyarados. Intimidate also becomes a deadly factor to Skarmory since after Gyarados switches in, Skarmory is often forced to switch.