Brutal Severity

Your battle prowess is felt in the field. Upon scoring a critical hit, your melee weapon attacks do one of the following:

Bleeding:

With slashing weapons, you slice open a wound in the creature, causing them to bleed. The creature must succeed a Constitution saving throw equal to 10 + Proficiency bonus + Attacking  Modifier, or be bleeding for 1 minute. On a fail, the creature takes bleeding damage equal to 1d6 at the start of every round. This affect end early if the creature is healed. This affect does not apply to Constructs, Elementals, Oozes or Undead.

Puncture:

With piercing weapons, the DM must decide where on the creature the weapon dealt damage to, depending on the body part, the creature suffers an affect. The affect is removed if the creature is healed by a spell that restores loss of body parts, or something similar. Does not affect Oozes.

Arm/Hand/Attacking Limb: -2 to Strength
Leg/Feet/Walking Limb/Wing : -2 to Dexterity
Torso/Chest/Back: -2 Constitution, the creature also suffers damage equal to the health lost as a result of this
Head: -2 to Intelligence, Wisdom or Charisma, up to the DM

Sunder:

With bludgeoning weapons, the force of the blow cracks, weakens or otherwise damages the creatures armour, carapace, exoskeleton or other physical outsides of creatures. The creature suffers a -2 to AC. This affect is removed by Mending if it affects armour, or by any healing spell that restores missing body parts. Does not affect Elementals. Constructs and Earth Elementals suffer -3 to AC instead.