Great Weapon Master

You’ve learned to put the weight of a weapon to your advantage, letting its momentum empower your strikes. You gain the following benefits:

• 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 heavy weapon that you are proficient with, you can choose to take a penalty on your attack roll which sees you not adding your Proficiency Bonus to your attack roll, and gaining a bonus to damage for this attack equal to double your Proficiency Bonus.