Brutal Critical (2 dice) is a Barbarian feature gained at level 13 in D&D 5e. Beginning at 9th level, you can roll one additional weapon damage die when determining the extra damage for a critical hit with a melee attack.
Beginning at 9th level, you can roll one additional weapon damage die when determining the extra damage for a critical hit with a melee attack. This increases to two additional dice at 13th level and three additional dice at 17th level.