Azurill is a glass cannon on a timer. It hits with devastating power, but can't take a hit to save its life. Azurill functions incredibly well in Trick Room, dealing massive amounts of damage while outspeeding most foes. However, it needs support to do its duty, which is a considerable weakness. If you're tired of the old Trick Room sweepers and want to try something new, Azurill can hit everything hard with only minor amounts of prediction. Nothing in Little Cup can survive two hits from Azurill.
Azurill has two useful attacks, given its stats: Return (or Double-Edge) and Waterfall. Thankfully, these moves together provide perfect neutral coverage and operate off of Azurill's massive 24 Attack.
The choice between Return and Double-Edge comes down mostly to preference. Double-Edge has massive power, but destroys any chance at all of Azurill surviving any attack, even weak hits. Return has less power, but lets you conserve more of Azurill's HP. Ghost- and Steel-types that resist Azurill's chosen Normal-type attack are hit by Waterfall for massive damage. Iron Tail OHKOes all Lileep after Stealth Rock if Azurill is running Life Orb. Encore allows Azurill to punish those that try to use setup moves, letting it fire off a powerful attack without fear of retaliation. Substitute is a great choice for the last slot; the switches that Encore can force allow Azurill to safely set up a Substitute and proceed to KO the opponent's Pokemon at no risk to itself.Team Options & Additional Comments >>>
Body Slam is a decent option, but the substantial power loss outweighs the paralysis rate. Knock Off can get rid of an opponent's item while doing semi-decent damage, especially to Ghost-types. Special attacks are largely pointless, as Return and Waterfall together grant enough power and coverage to make Hidden Power redundant. Sing is an option, but its low accuracy is off-putting. Azurill can also set up Rain Dance itself. It has some notable stat-reducing moves in Charm and Tickle, but it is usually better off doing as much damage as possible.
Checks and Counters
Azurill is a Normal-type with powerful Water-type attacks. This makes countering it directly quite difficult because one of its two attacks will hit your switch-in like a truck. Your best bet is to send in a Ghost-type or a Pokemon with a Water-type immunity and hope for the best.
Revenge killing Azurill is fairly simple, however; most priority attacks will keep it in check. Croagunk has Vacuum Wave, which can easily finish off Azurill after Life Orb recoil. Munchlax or Trapinch built around Trick Room will also be slower than Azurill, allowing them to outpace it. If rain is up, Aqua Jet works pretty well. If Trick Room isn't active, nearly anything with decent offensive power that outspeeds Azurill will do the job.