Whimsicott

Whimsicott is the fastest Pokemon with the ability Prankster; this, coupled with its expansive support movepool, makes it a niche choice for a disrupter and Tailwind setter. However, Whimsicott has a myriad of flaws that can hold it back from performing its role in the Doubles OU metagame. For starters, Whimsicott has almost no offensive presence, leaving it able to do real damage only against targets that are weak to its STAB moves. Whimsicott's defenses are also lackluster, forcing it to equip a Focus Sash and making it tough for it to stay on the field and perform its role for more than a couple of turns. Furthermore, Whimsicott's typing is not very good defensively, as it is weak to common Ice-, Fire-, and Flying-type moves. Finally, Whimsicott is almost wholly outclassed by Thundurus and Talonflame. Thundurus also has Prankster but, unlike Whimsicott, also boasts a good typing and offenses, while Talonflame has priority Tailwind and a great offensive presence.