So, Darkrai is pretty good in Ubers. Though the Dark Void nerf made it less used in Ubers. There are a few things around this, but it's not easy. First set, we have the classic Z-Hypnosis Darkrai.
Darkrai @ Psychium Z
Ability: Bad Dreams
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
- Hypnosis
- Nasty Plot
- Dark Pulse
- Focus Blast / Sludge Bomb
This has a 40% chance to fail. First turn, use Z-Hypnosis to put the opponent to sleep and get a speed boost. Then, whether they switch out or not, use Nasty Plot. You now have +2 Sp. Atk and +1 Speed. Dark Pulse is for your main STAB. Focus Blast is for other Darkrai, while Sludge Bomb is for unboosted Xerneas.
Now, here's my second set for Darkrai. Sub-Nasty Plot.
Darkrai @ Leftovers
Ability: Bad Dreams
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
- Substitute
- Nasty Plot
- Dark Pulse
- Focus Blast / Sludge Bomb
This is similar to the last set. First turn, use Substitute and hope they don't attack you. Then, use Nasty Plot to boost your Sp. Atk. Dark Pulse is STAB. Focus Blast and Sludge Bomb are for the same purpose as last set.