I might be a new person, but I am the master of stall sweeping teams. Check this moveset out.
Dark Void- much more accurate than hypnosis, which is 60 accuracy compared to 80. It makes use of darkrai's ability and puts foe to sleep.
Double team- While the opponent is sleeping, you are able to set up double team, making this guy hard to hit.
Nasty Plot- Raises special attack by 2 stages, after nasty plot and double team maxed, your opponent is completely screwed.
Dream Eater- The signature move for darkrai, great power and works well with dark void, also allows darkrai to regain health.
EV's- 252 SAtk 252 Spd 4 HP
Ability- Bad dreams
Darkrai is an amazing pokemon that is capable of sweeping an entire team. Even though his only attacking move is dream eater, which won't do much to steel, or have no affect on dark, Darkrai's ability will eventually cause the opponent to attack and once darkrai is set up with maxed out nasty plot, anything resistant to dream eater still stands no chance. The only threat to this moveset would be a Dusknoir with something like shadow punch. Even considering all of this, shadow punch wouldn't do very much and leftovers should provide enough health coverage so that any opponent would fall after 8 turns.