Whimsicott

Whimsicott is a cute little cottonball of a Pokemon, and it's about as threatening as a cottonball in practice.

On offense, it's horribly outclassed in as both a Fairy and Grass Type, having an attack stat far too low to be genuinely useful. On defense, it has issues with its middling defensive stats, as well as the fact that Steel Types wall its entire moveset, making it extremely vulnerable to Metagross in particular.

It's probably best to not spend stardust on Whimsicott....

Best PvE Offensive Moveset

• Charm or Fairy Wind and Moonblast can make Whimsicott a Fairy attacker
• Razor Leaf and Grass Knot can make Whimsicott a Grass attacker
• Hurricane has no real utility on offense.

Best PvE Defensive Moveset

• Charm is the fast move of choice for defense, sporting outstanding defensive performance, STAB, and good neutral coverage.
• Razor Leaf is definitely the weaker option here.
• Seed Bomb is Whimsicott's cheapest charged move, and the only move that it's likely to use on defense.
• Grass Knot falls behind when compared to Seed Bomb
• Hurricane and Moonblast are too expensive and unlikely to be used.

Fairy Wind provides Whimsicott the energy gain to reach its rather expensive Charged Attacks and utilize its rather unique coverage.

Both Charm and Razor Leaf sport the highest damage output from fast moves in the game, but also tie for the worst energy generation. Charm is generally preferred, as many other Grass-type Pokemon have access to Razor Leaf.

Seed Bomb costs the least amount of energy among Whimsicott's charge moves and benefits from STAB, but its damage can be lacking. Charm Whimsicott should run Seed Bomb to compensate for Charm's low energy gain. Grass Knot costs slightly more energy but deals considerably more damage; it is the preferred Grass option if running Fairy Wind. Moonblast costs 5 less energy than Hurricane, but both are very slow to access and are different typings. Either can be chosen, though poor energy generation may limit access to them.