Notes:

For those who don't understand the analogy, please read here:

Any person who has played TF2 will know that the Stickybomb launcher is one of the best weapons on the game. Powerful as hell, can decimate teams who aren't prepared and is really spammable. However, it's not a broken weapon. For example, it has long reload times, which can leave you open to spies and snipers if you're not careful.

Now let's look at Darkrai: It's a very fast special attacker and it's most used tactic is putting the target/s to sleep with Dark Void, then spamming your desired move against them whilst they take additional damage per turn from Darkrai's ability, Bad Dreams. Whilst I'm most likely going to get killed to death for saying this, I don't think Darkrai is THAT overpowered. I mean, it's kinda OP, but not to the extent as some people make it out, as in, thinking it's unstoppable.

Firstly, Darkrai's move for putting foes to sleep has 80% accuracy, only slightly more than Sleep Powder. If it misses, you leave yourself wide open for an attack that'll most likely OHKO it due to it's very lackluster Defenses and HP. Secondly, the Sleep Status can be bypassed/averted by pokemon with Vital Spirit/Insomnia as their ability or those holding a Chesto/Lum berry.

Well, that's my overall opinion on this Pokemon. I do own one, mind you. But I only use it on my team when I want to give some people on the PSS a hard time.
P.S – I don't play this game competitively, though I have a fair amount of experience with Pokemon (9 years almost). My opinions are based on my personal experience of using and going against it.

Thank you and good night.