Hamstring

Ryoko's Guide to the Yokai Realms
Loot Tavern

In a vicious attack, you attempt to debilitate an enemy. Make an attack roll against a creature within your reach. On a hit, the target suffers the attack’s normal effects and takes extra damage equal to your proficiency bonus. In addition, until the end of its next turn, the creature’s AC is reduced by a value equal to its Dexterity modifier (minimum 0), and its speed is reduced by a number of feet equal to 5 times your proficiency bonus (to a minimum of 0 feet).