Lethal Duelist (5e Feat)
From D&D Wiki
Prerequisites: 13 Strength or 13 Dexterity
You are a an unparalleled master of fighting with a single weapon, honing the lethality of your strikes by targeting enemy weak spots almost as if it was second nature. Before you make an attack with a single handed melee weapon you are proficient with, if you are not wielding another weapon or a shield, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack’s damage.
Whenever you score a critical hit with a one handed melee weapon you are proficient with, if you are not wielding another weapon or shield, you may use your bonus action to make another melee attack with that weapon against the same target.