Azumarill

Huge Power
Doubles Attack.
Thick Fat
Halves Ice- and Fire-type damage.
Type Tier
Water UU
Level 100 Statistics (see level 5, 50, 100)
Min- Min Max Max+
HP
100
- 341 404 -
Atk
50
122 136 199 218
Def
80
176 196 259 284
SpA
50
122 136 199 218
SpD
80
176 196 259 284
Spe
50
122 136 199 218
Name Item Ability Nature

SubPunch

Leftovers Huge Power Adamant
Moveset EVs
~ Substitute
~ Focus Punch
~ Hidden Power Ghost
~ Sing / Encore
252 HP / 252 Atk / 4 Spe

This set is simple to use, but is Azumarill's standard set for a reason: it can be surprisingly effective. Water-types and Blissey will not be able to break Azumarill's Substitutes easily, letting it dish out extremely powerful Focus Punches in the meantime. Hidden Power Ghost grants it coverage on Gengar and other Ghosts, and should 3HKO most Dusclops. Sing and Encore can both buy Azumarill some extra time to use Substitute or Focus Punch.

24 Speed EVs enable Azumarill to outspeed Swampert. HP investment should be maximized for 101 HP Substitutes, which will survive Night Shade and Seismic Toss, but if forgoing Substitute, hitting a stat of 401 HP is fine. Finally, pump the rest into Azumarill's Attack.

Other Options

Hydro Pump or Surf can be used to beat physical walls such as Skarmory. Attract, as with Sing and Encore, can buy it free turns to use Focus Punch. Light Screen supports the team against the Electric-types Azumarill hates, while Charm and Tickle help against physically based foes. Icy Wind slows down opponents; while Azumarill might not be able to take full advantage of the Speed drops, its teammates might appreciate it. Perish Song forces switches, while Present is a fun gamble that will either hurt the crap out of your opponent, do shitty damage, or heal them. Azumarill is too slow to use Belly Drum effectively, but it's there.

Checks and Counters

Azumarill is flat-out walled by Weezing, and possibly by Claydol too, though Hidden Power Ghost and Hidden Power Water will hurt. Skarmory can take a few Focus Punches or Hydro Pumps. Gyarados and Salamence also wall Azumarill decently as they resist Focus Punch and can Intimidate it. Gengar is annoying if you don't use Hidden Power Ghost or Substitute on the switch, as he's immune to Normal and Fighting and often packs Thunderbolt. Lastly, if Azumarill doesn't have a Substitute up, Dugtrio can revenge kill it.