Ludicolo

Ludicolo is synonymous with rain; although rain only lasts five turns, Ludicolo can sweep through entire teams in that duration. Its ability Swift Swim doubles its Speed in rain, allowing Ludicolo to outspeed most other Pokemon. Although Ludicolo's offensive movepool is small, it has all it needs. Its STAB moves Hydro Pump and Giga Drain threaten common Pokemon like Rotom-W, Rotom-H, and Tyranitar for super effective damage. Dragon-types which would otherwise pose problems for Ludicolo, Salamence for instance, are OHKOed by Ice Beam. Ludicolo also has access to Rain Dish, which, alongside Ludicolo's good defensive typing and decent special bulk, can make it surprisingly hard to take down, especially when you factor in that most defensive sets use an Assault Vest. Fake Out is a staple move in Doubles, as it gives Ludicolo the option of stopping one of the enemy Pokemon for a turn.

Regardless of the set, Ludicolo is dependent on rain, and thus Politoed by extension. Ludicolo has a mediocre Speed stat outside of rain, so many Pokemon threaten it; this is very limiting to teambuilding. As Ludicolo will almost always run the same moves, regardless of set, it can be very predictable. Although Ludicolo has good Special Defense, its Defense is lackluster. Talonflame's ever-present Brave Bird causes huge problems, as it can easily OHKO Ludicolo. Even with Ice Beam, Ludicolo has problems with common bulky Grass-types like Ferrothorn, Mega Venusaur, and Amoonguss.