Dark Haunter.

Put a Baby Pokémon or Basic Pokémon card from your opponent's discard pile onto his or her Bench. Put 1 damage counter on that Pokémon. (You can't use this attack if your Bench is full.)

Flip a coin. If heads, the Defending Pokémon is now Asleep. If tails, the Defending Pokémon can't retreat during your opponent's next turn.