Heavy Weapon Master Feat

You are an expert at using heavy weapons. When you wield a weapon with the heavy property, you gain the following benefits:

Prerequisite: Proficiency with melee weapons that have the heavy property

• Heavy Strike. When you make a melee weapon attack with a weapon that has the heavy property that you are proficient with, you can forgo adding your proficiency bonus to the attack roll. When you do so and hit, the attack deals additional damage equal to twice your proficiency bonus.
• Brutal Momentum. When you make a melee weapon attack with a heavy weapon on your turn that rolls a critical hit or reduces a creature to 0 hit points, you can make one melee weapon attack with the same weapon as a bonus action.

Source: KT