Pros:
+Unique Grass/Water typing leaves it with weaknesses to only flying, poison, and bug, making it a great addition to rain teams since it shares no weaknesses with other water types
+Swift Swim has made Ludicolo a rain team staple since forever, able to pump out high-powered water attacks while outspeeding the competition
+90 special attack is passable when boosted by rain, and 100 special defense is deceptively bulky
+Access to Fake out and a large number of other offensive moves gives Ludicolo a home in doubles
Cons:
-70/90/70 offenses isn't that impressive even under rain, and if not using a rain-boosted water-type move Ludicolo's lack of power is noticable
-80/70/100 bulk with weaknesses to flying, bug and poison leave Ludicolo vulnerable physically
-Seismetoad, Mega Swampert and Kingdra are all faster swift swim users, giving Ludicolo some serious competition
Abilities:
Rain Dish: Heals 1/16th max hp at the end of each turn while it is raining. Basically a second leftovers, it can be very useful to keep Ludicolo healthy when combined with other forms of recovery like leftovers and leech seed.
Swift Swim: Doubles Ludicolo's speed in rain. This makes Ludicolo a very potent special threat, capable of outspeeding key threats and punching holes through walls.
Own Tempo: Prevents Ludicolo from being confused. Outside of Hurricane, confusion is pretty uncommon, and not taking either of Ludicolo's rain-orientated abilities takes away its niche and thus the entire reason to use Ludicolo in the first place.
Sets
Z-move Attacker
Nature: Modest/Timid
Ability: Swift Swim
Ev's: 4 HP / 252 Spa / 252 Spe
Item: Waterium-Z/Life Orb
Moves:
-Hydro Pump/Scald
-Energy Ball
-Ice Beam
-Fake out/Protect
This is the most common Ludicolo set you will see. Hydro pump hits like a truck under rain, but the low accuracy can make it a little bit risky, so you can opt for Scald if accuracy is more important, but the lower power will be noticeable. Energy ball is the grass-STAB and hits mega Swampert, the prime swift swim user in VGC 2018. Ice Beam offers fantastic coverage against Garchomp and Landorus-T. Fake out is great in doubles to pop a focus sash or buy an ally a turn to set up or switch in with less worry. Modest is the preferred nature since it offers the most power, although timid is a viable option to outspeed opposing Ludicolo and catch other faster threats by surprise.
Ludicolo's weaknesses to poison, bug and flying means it needs to watch out for Garchomp's Poison jab, Pelipper's Hurricane, and various U-turn abusers. Obviously, a drizzle user is a mandatory team mate. Pelipper offers a nice flying/water typing and provides more offensive presence than politoed, and has perfect accuracy Hurricanes under rain. Additional Pokemon that appreciate rain dance include Mega Swampert as a second swift swimmer, or electric types like Tapu Koko that can abuse perfect accuracy Thunders under rain.
Assault Vest
Nature: Modest
Ability: Swift Swim
EVs: 204 HP / 20 Def / 124 SpA / 76 SpD / 84 Spe
Moves:
- Scald
- Giga Drain
- Ice Beam
- Fake Out
A bulkier EV spread with an assault vest makes Ludicolo very difficult to take down, and the increased bulk allows Ludicolo to make use of more defensive attacks like Giga Drain to keep itself healthy, or Scald to snag a burn on an opponent. The speed Ev's allow it to outspeed Timid Tapu Koko under rain, and makes its thunderbolt a 3HKO. Giga Drain also hits Mega Swampert, as well as Rotom-W super effectively. Weather control is important, because outside of Rain Ludicolo slows down to a crawl, and hits like a pool noodle.
Good allies for Ludicolo besides the obvious rain setters include team mates that can beat opposing rain teams. Powerful electric types like Tapu Koko or Mega Manectric come to mind, but they are walled by grass and ground types. An additional grass type like Ferrothorn or Mega Venusaur make for good checks to Mega Swampert, and appreciate rain support to cover their Fire-type weaknesses. Just watch out for Pelipper's hurricane, scaring off grass types that might want to switch in. Lightning rod users like Raichu or Togedemaru can keep your other water types and rain setters safe from single-target electric attacks. Intimidate abusers can shore up Ludicolo's lesser physical defense.
