Bone Breaker (5e Feat)
From D&D Wiki
You have trained hard to master unarmed combat.
- Your unarmed strikes score a critical hit on roll of 19-20.
- When you score a critical hit with an unarmed strike, you can roll one of the your damage dice one additional time and add it to the extra damage of the critical hit.
- When you score a critical hit with an unarmed strike, the target must make a Constitution saving throw (DC = 8 + your Strength or Dexterity modifier + your proficiency bonus). If they fail, choose one of the following effects: