Unarmed Combat Master

Forgoing the usage of normal weaponry, you've honed your body into becoming a weapon of its own. You gain the following benefits:

• Increase your Strength or Dexterity score by 1, to a maximum of 20.
• On your turn, when you score a critical hit with an unarmed strike or reduce a creature to 0 hit points with one, you can make one unarmed strike attack as a bonus action.
• Before you make an unarmed strike attack, you can choose to take a -4 penalty to the attack roll. If the attack hits, you add +8 to the attack's damage.