Crippling Assault is an encounter power available to the Barbarian class at level 27.[PrP:23]
Crippling Assault
Barbarian Attack 27
Melee weapon
Target: one creature
Attack: Strength vs AC
Hit: 4[W] + Strength modifier damage, and the target gains vulnerable 5 to all damage until the start of your next turn.
Thaneborn Triumph: The vulnerability equals 3 + your Charisma modifier
Special: When charging, you can use this power in place of a melee basic attack.