Here is the best board clear spell in the K&C set. Don't worry that it doesn't destroy the enemy's minions but shuffles them into their deck, as the effect is still incredibly powerful.
For example, consider facing an Aggro Druid that plays Living Mana. With the help of Pyschic Scream, you will put all of the Mana Treants into your opponent's deck without actually restoring the mana crystals. This will instantly break their game and grant you a victory.