.Bright Side.
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Prankster Thunderus's Taunt shuts down any Whimsicott set.
When Whimsicott has no speed EVs. With 216 Speed EVs and a positive speed nature, Thundurus gets screwed... wait no it doesn't, if it has HP Ice.
But you need to be careful with Cloyster. It's weak to grass, and since whimiscott has higher speed, it could Probably OHKO or 2HKO it.>Cloyster
If Cloyster comes in on Whismicott, it can revenge it with Icicle Spear. However, if Whismicott comes in on a Cloyster as it Shell Smashes, they can encore it and shut it down.
But you need to be careful with Cloyster. It's weak to grass, and since whimiscott has higher speed, it could Probably OHKO or 2HKO it.
If it's a OHKO, cloyster won't be able to counter it.
For a counter what about a dream world Espeon or Xatu?
People won't willingly trade Bold nature and def/spdef Evs for something made obsolete by prankster and for a single counter.
Well, some of the sets here actually run speed EVs... not like I know why though. Never used Whimsicott, never will.
And that counter is quite common too. Or at least pretty common. I dunno.
Some don't want to be shut down by taunt.Except that it's best for Whismicott not to run any offensive moves.