What a Rush

The hardest part is getting the valkyries to go for the inside instead of the outside. After using archers and poison to deal with CC troops, drop the barbarian king somewhere that has minimal surrounding pieces outside the wall and is near a defense (preferably a splash one like mortar or wizard tower, we want to kill those first). (If necessary, have a few archers and 1-2 Valks cleanup the surrounding outside area). Then drop a rage/heal combo rush of your Valkyries to break down the first wall and get inside to tear the base apart.

At your discretion use the final heal spell on the Valkyries to keep their health high so they can finish off the base.