Great Weapons Master

When attacking with a "heavy" weapon you are proficient with, you can -5 from the attack roll and if it hits add +10 to damage modifier for this attack only.

If a critical is made with a melee weapon or reduces a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.

This was created for people who want the "Great Weapons Master" feat but don't want to buy the player's handbook.