Single Hand Weapons Master

You've reached peak capability of elegantly handling your weapons with one of your hands, knowing when to strike and where. You gain the following benefits to one hand of your choice (right or left hand): 

• On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.
• Before you make a melee attack with a finesse weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.