Gyarados

Flying

Gyarados's high Attack stat and access to Dragon Dance allow it to be a potent setup sweeper. Its Water typing is helpful against Rock and Ice teams, which are usually problematic for Flying. A great ability in Moxie improves Gyarados's sweeping potential even further by boosting its Attack every time it gets a KO, and its solid bulk allows it to set up more easily. However, while Bounce is a decent STAB move, its charging turn requires Gyarados to use a Flyinium Z to break past bulky Grass-types such as Mega Venusaur. Gyarados's Water typing can be useful in some situations, but it also has its drawbacks, as it gives an even bigger Electric weakness to Flying teams. Though base 81 does put Gyarados at a unique Speed tier, allowing it to barely outspeed base 80 Speed Pokemon such as Dragonite, it is overall mediocre, preventing Gyarados from outspeeding some Pokemon even at +1, such as Mega Alakazam. Gyarados can also lose to many common Choice Scarf users such as Nihilego and Xurkitree. Finally, Gyarados can be outclassed in some situations by other Z-Move users such as Salamence and Landorus-T, but it does hold a niche over them due to its access to Taunt, which allows it to not be walled by certain bulky Pokemon and set up against them.

Water

Gyarados is one of the strongest Pokemon on Water, breaking huge defensive threats such as Mega Venusaur and Ferrothorn with a boosted Supersonic Skystrike. It has access to two good abilities, Moxie and Intimidate. The former improves Gyarados's sweeping potential after it gets a KO, while the latter allows it to set up more easily on physical attackers. Gyarados's decent bulk in conjunction with Intimidate gives it almost no problem setting up, as it can take most weaker neutral attacks easily. However, Moxie is generally more useful because Gyarados has a much easier time snowballing teams without having to Dragon Dance multiple times to get vital KOs. Gyarados has access to Taunt, which means it can set up on phazers such as Skarmory or walls looking to cripple it with status such as Gastrodon. Gyarados's typing gives it a good number of useful resistances to types such as Fighting and an immunity to Ground-type moves. It notably takes only neutral damage from Grass-type attacks but has a crippling weakness to Electric-type attacks. It is also immune to Toxic Spikes and Spikes. Gyarados can outpace the majority of unboosted Pokemon, notably Tapu Koko and Mega Lopunny, at +1. However, Gyarados's Speed stat leaves much to be desired, as before setup it is very susceptible to attacks from faster Pokemon such as Kyurem-B; even at +1, it is still easily revenge killed by faster Choice Scarf Pokemon such as Victini. Gyarados also has a hard time setting up in certain matchups and gets outright walled by Pokemon such as Rotom-W; other factors, such as its weakness to Stealth Rock, can also make setting up difficult. Bounce takes a turn to charge, which makes it useless against Pokemon such as Baneful Bunker Toxapex and Protect Ferrothorn after Flyinium Z has been used.