Brutal Critical (1 die)

Class featurePHBp. 462014SRDBarbarian

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.

Raw data
{
  "srd": true,
  "name": "Brutal Critical (1 die)",
  "page": 46,
  "level": 9,
  "__prop": "classFeature",
  "source": "PHB",
  "entries": [
    "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."
  ],
  "className": "Barbarian",
  "classSource": "PHB"
}