Anyway with that clickbait toplevel out of the way, here is the story about how funny paint dog destroyed the Lord of Nightmares

Darkrai is: A mythical Pokemon with a signature move, Dark Void that make things sleep

Smeargle is: goofy dog thing that can learn any move

The scene is Generation VI. The format for official Pokemon tournaments is VGC, which is Doubles But More Complicated

Dark Void has a special property in that in double battles, it can hit both opponents

Darkrai is not allowed in VGC but do you know who is allowed? Smeargle.

Smeargles running Dark Void are common and are used to put opposing teams to sleep, as Dark Void not only targets both opponents, but it has 80% accuracy

So lots of things go sleepy, things get lame for doubles

No one wants to watch or play with or against Smeargle Dark Void Spam

But there's not much that can be done about that for now

Anyway, the generation wheel turns and it is now Generation VII

They want to make extra sure that Smeargle Dark Void Spam will not be a thing next time around

So they change the coding in the game so that only Darkrai (or a Pokemon that has transformed into Darkrai) can successfully use Dark Void, if any other mon tries to use it, it fails

Technically you can still use it via Metronome but w/e

So problem solved right

VGC usually only allows select legendaries/mythicals to be used so just don't let Darkrai in boom

Darkrai is now the only mon that can use Dark Void (its signature attack) and if you don't want sleep spam just don't let it in

NAH SON

They went a step further

Dark Void also has been reduced to 50% accuracy

making it the most inaccurate sleep move in the game (not counting weird outliers like Relic Song and Dire Claw)

So now Darkrai's Signature Move is now just really bad

The mon that's all about making things go to sleep now sucks at making things go to sleep

If Darkrai wants to put something to sleep, it's better off using Hypnosis because Hypnosis is 5% more accurate than Dark Void

And this all happened because Smeargle was using Dark Void willy nilly in VGC

Darkrai died for Smeargle's sins also Smeargle is a habitual criminal it is like constantly causing issues in Pokemon PvP regardless of format