As long as Slaking is your Active Pokémon, any damage done by attacks from your opponent's Pokémon-ex is reduced by 30 (before applying Weakness and Resistance).

Amnesia20

Choose 1 of the Defending Pokémon's attacks. That Pokémon can't use that attack during your opponent's next turn.

Lazy Headbutt70

Slaking is now Asleep.