Unarmed Master (5e Feat)
From D&D Wiki
You have become a master at unarmed fighting using your fists to wreak havoc upon those who have wronged you...
Before you make an unarmed strike, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.
Additionally the size of your unarmed strike becomes one die size larger (d4->d6, etc.). If you do not already have roll for the damage of your unarmed strikes, it becomes a d4.