And just when you thought you got away from Moxie Max Airstream Strats... Gamefreak pulls you back in...
Quaquaval's Aqua Step completes the tri-fecta of absurd starter STABs. What was once a decent sweeper let down by its slightly below average speed, Quaquaval's signature move instantly catapults it into terrifying late-game sweeper territory able to escalate out of control after picking up a single KO.
However, Quaquaval has some serious issues. Water Fighting is a great STAB combination, but several popular walls like Toxapex, Slowbro, and Amoongus wall its STABs, with Terablast Electric being the only recourse for Toxapex. Azumarill threatens unless Quaquaval is at +3 (or +2 with entry hazards) Dondozo is also problematic. While STAB Close Combat does sting:
252 Atk Life Orb Quaquaval Close Combat vs. 252 HP / 4 Def Dondozo: 212-251 (42 - 49.8%) -- guaranteed 3HKO
Quaquaval will tear itself apart to do so while Dondozo will Curse and Rest it off, winning the war of attrition (it needs to come after a KO or its slow speed would just make it another KO). Additionally, Palafin being such an excellent Pokémon near invalidates every other offensive water type, which is already a crowded field with Azumarill, Cloyster, Gyarados and others all vying for the top spot.
Quaquaval's lackluster speed is still a pain point. Until it sets up a single Aqua Step, outspeeding it is rather easy. After a Single Aqua Step it still loses to every faster Choice Scarf user.
Substitute -Foils attempts to status Quaquaval, but for best effect has to be run with Swords Dance, and you are giving up valuable coverage to do so.
Rapid Spin -Entry Hazard removal is at a premium in this generation and while Corviknight and Great Tusk are the gold standards, but other options are worth consideration.
Brave Bird -Chunks Amoongus and Annihilape... and Quaquaval. Also so happy this isn't Gen 8 cause Max Airstream from Quaquaval is a terrifying thought -it has enough methods to boost its speed as it is.
Baton Pass -As if Quaquaval isn't hard enough to deal with as it is when it can pass its boosts to a teammate.