Bone Breaker (5e Feat)

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:
- The target has disadvantage on attack rolls until the end of their next turn.
- The target is knocked prone.