Jawbreaker

Prerequisite: Proficiency with a weapon that deals bludgeoning damage. 

You have mastered the art of bashing the ever living crap out of your enemies faces, whether with a bludgeoning weapon or your fists.

• Increase your Strength or Dexterity by 1, to a maximum of 20.
• Whenever you hit a creature that has a bite attack with a bludgeoning weapon or your fists. You knock out some teeth in the process. On a hit, the creature takes a damage penalty from their bite attack. 
• The penalty is based on half your proficiency bonus, rounded up. (Minimum of 1). (This effect does not stack)
• If you roll a natural 20 on an attack roll,  the creature must make their damage rolls with disadvantage, if it involves a bite attack.