#Have your pet Wraith turn the dead creature into a Specter and then kill the Specter#

#Necrotic Damage could potentially damage the soul enough that it is destroyed on death#

#Ensure your target is evil and employ a Night Hag assassin#

#Have a Barghest feast on the corpse#

#Have your pet Lich feed the soul to its phylactery#

#Summon an Avatar of Death to slay the creature#

Have your pet Wraith turn the dead creature into a Specter and then kill the Specter

Necrotic Damage could potentially damage the soul enough that it is destroyed on death

Ensure your target is evil and employ a Night Hag assassin

Have a Barghest feast on the corpse

Have your pet Lich feed the soul to its phylactery

Summon an Avatar of Death to slay the creature

#Have your pet Wraith turn the dead creature into a Specter and then kill the Spectre#

A Wraith can use its action to turn a recently slain humanoid into a Specter:

Create Specter. The wraith targets a humanoid within 10 feet of it that has been dead for no longer than 1 minute and died violently. The target''s spirit rises as a specter in the space of its corpse or in the nearest unoccupied space. The specter is under the wraith's control. The wraith can have no more than seven specters under its control at one time.

The specter has this description in its stat block:

In the players handbook Necrotic damage is described thus:

Necrotic. Necrotic damage, dealt by certain undead and a spell such as chill touch, withers matter and even the soul.

Night Hags have the following feature:

Nightmare Haunting (1/Day). While on the Ethereal Plane, the hag magically touches a sleeping humanoid on the Material Plane. A protection from evil and good spell cast on the target prevents this contact, as does a magic circle. As long as the contact persists, the target has dreadful visions. If these visions last for at least 1 hour, the target gains no benefit from its rest, and its hit point maximum is reduced by 5 (1d10). If this effect reduces the target’s hit point maximum to 0, the target dies, and if the target was evil, its soul is trapped in the hag’s soul bag. The reduction to the target’s hit point maximum lasts until removed by the greater restoration spell or similar magic.

The Barghest Soul Feeding feature has the following text:

During that 24 hours there is a 50% chance the humanoid can be resurrected on each attempt of revival, but only by a spell that works without the complete original body (so Reincarnate, Resurrection or True Ressurection).

#Have your pet Lich feed the soul to its phylactery# A lich can sacrifice a soul to its Phylactery, and after 24 hours the soul is destroyed by the Phylactery. The only way to free the soul is to find the Phylactery and cast a 9th level dispel magic on it, within the 24 hour time limit.

Source: Monster manual entry on a Lich:

Soul Sacrifices. [...] A creature imprisoned in the phylactery for 24 hours is consumed and destroyed utterly, whereupon nothing short of divine intervention can restore it to life.

The Deck of Many Things gives the Stat Block for an Avatar of Death, and contains this sentence about one of its unique properties:

#Have your pet Wraith turn the dead creature into a Specter and then kill the Specter#

A Wraith can use its action to turn a recently slain humanoid into a Specter:

Create Specter. The wraith targets a humanoid within 10 feet of it that has been dead for no longer than 1 minute and died violently. The target''s spirit rises as a specter in the space of its corpse or in the nearest unoccupied space. The specter is under the wraith's control. The wraith can have no more than seven specters under its control at one time.

The specter has this description in its description in the Monster Manual:

In the Player's Handbook (p. 196), necrotic damage is described thus in the "Damage Types" section:

Necrotic. Necrotic damage, dealt by certain undead and a spell such as chill touch, withers matter and even the soul.

Night Hags have the following feature:

Nightmare Haunting (1/Day). While on the Ethereal Plane, the hag magically touches a sleeping humanoid on the Material Plane. A protection from evil and good spell cast on the target prevents this contact, as does a magic circle. As long as the contact persists, the target has dreadful visions. If these visions last for at least 1 hour, the target gains no benefit from its rest, and its hit point maximum is reduced by 5 (1d10). If this effect reduces the target’s hit point maximum to 0, the target dies, and if the target was evil, its soul is trapped in the hag’s soul bag. The reduction to the target’s hit point maximum lasts until removed by the greater restoration spell or similar magic.

The Barghest's Soul Feeding sidebar (VGtM, p. 123) has the following text:

During that 24 hours there is a 50% chance the humanoid can be resurrected on each attempt of revival, but only by a spell that works without the complete original body (so Reincarnate, Resurrection or True Resurrection).

#Have your pet Lich feed the soul to its phylactery#

A lich can sacrifice a soul to its Phylactery, and after 24 hours the soul is destroyed by the Phylactery. The only way to free the soul is to find the Phylactery and cast a 9th level dispel magic on it, within the 24 hour time limit.

Source: Monster Manual entry on a Lich (p. 203):

Soul Sacrifices. [...] A creature imprisoned in the phylactery for 24 hours is consumed and destroyed utterly, whereupon nothing short of divine intervention can restore it to life.

The Deck of Many Things gives the stat block for an Avatar of Death, and contains this sentence about one of its unique properties: