Since the ban of Drizzle + Swift Swim, Ludicolo has yet to break away from the depths of NU. Losing its most valued asset, one may wonder why Ludicolo should ever be used in the OU tier again. The answer lies in Ludicolo's new role in the metagame, manual rain teams; Ludicolo can then reach its full potential as a solid special sweeper. With a great offensive and defensive Water / Grass typing, along with a respectable movepool, Ludicolo is more than capable of finding plenty of opportunities to switch in and wreak havoc. However, Ludicolo is the epitome of a niche Pokemon; your entire party should be devoted to setting up rain independently, or it will be of little-to-no use when adding it to your team. Despite these drawbacks, it is imprudent to underestimate a Ludicolo in the rain, as it will decimate your team if given the chance.
Ludicolo excels as one of the best special sweepers for manual rain teams. Hydro Pump is the go-to STAB of choice; thanks to its high base power, which is further increased by rain and Life Orb, anything that does not resist it will face a 2HKO at worst and an OHKO at best. Giga Drain is the more reliable STAB attack that allows Ludicolo to break through bulky Water-types such as Jellicent and Vaporeon, something its partner Kingdra can't do as easily. Ice Beam rounds out the coverage and hits troublesome rain checks such as Celebi and Dragonite for super effective damage. The final slot is a matter of preference regarding either support or more power. Ludicolo can set up Rain Dance autonomously, which allows it to support its teammates and disrupt the momentum of opposing weather teams, in particular i.e. sand, hail, and sun. Focus Blast on the other hand allows Ludicolo to break through Ferrothorn and the Kyurem formes, which otherwise wall it to no end.Team Options & Additional Comments >>>
Despite its vast movepool, Ludicolo can't really make much use of what it has. A physical Swords Dance set is possible, but between setting up Rain Dance and finding an opportunity to pull off a Swords Dance, it's too strapped for time and will likely have taken too much damage to get a sweep going. A SubSeed set with Rain Dish is also plausible, but there are far too many Pokemon that can simply break through it. Moreover, Ludicolo has neither the have the bulk nor power to abuse it. Finally, a mixed Hone Claws set can also be used, though it experiences the same complications as the Swords Dance set.
Checks and Counters
As with most weather-orientated sweepers, altering their favored weather condition drastically decreases their performance. In Ludicolo's case, it loses its blistering speed and its Water-type attacks weaken, making it susceptible to more powerful attackers. Specially defensive Ninetales is a good check, as it does all the above and can proceed to 2HKO it with Flamethrower. Abomasnow, Tyranitar, and Hippowdon have difficulty switching in, but their ability to change the weather is invaluable.
Blissey and Chansey are above all the best counters to Ludicolo. They can easily sponge any attack and gradually wear it down with Toxic and repeated Seismic Tosses. If Ludicolo lacks Focus Blast, Ferrothorn and the Kyurem forms are also great counters, being able to switch into all attacks and 2HKO with Power Whip and Ice Beam, respectively. Defensive Latias, Celebi, and Toxicroak are also decent checks, all three of them can switch in relatively easily and only have to watch out for Ice Beam. Specially defensive Jirachi can tank a single hit and attempt to paralyze Ludicolo and Tentacruel can potentially stall it out with Toxic + Protect.
Despite Ludicolo's blistering Speed in the rain, it falls short of outspeeding base 110+ Choice Scarf users. As such, Choice Scarf Latios is a great check, even being able to switch in once on Ice Beam - from there, it can outspeed and OHKO with Draco Meteor. Choice Scarf Gengar and Starmie don't have the same power, but can potentially take out a weakened Ludicolo. In the same vein, powerful priority users such as Breloom, Dragonite, Mamoswine, and Lucario can also take out a damaged Ludicolo. If Ludicolo decides to go for a positive attacking nature, then even base 100+ Choice Scarf users can deal with it, the most notable being Garchomp and Thundurus-T.