Answer 1

Primeape is considered the best counter to Darkrai due to Vital Spirit and being a Fighting type. However, any Pokemon with Sleep Talk makes a counter to Darkrai. Mewtwo counters Darkrai due to higher Speed and Aura Sphere.

Comments

Me I used a Noctowl (with insomnia) because I hadn't primape.. It's also good.

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Unfortunately many Darkrai carry Ice-beam so Noctowl would not do well.