General:
* Infernal: relating to or characteristic of hell.
* Abysmal: extremely bad; appalling.
* Damned: condemned to hell; utterly hopeless.
* Cursed: under a divine curse; doomed to suffering.
* Tormenting: causing great pain or suffering.
* Devastating: causing great destruction or damage.
* Desolate: completely empty or deserted; without life or hope.
* Grim: dark and depressing; forbidding.
* Dreadful: causing fear or dread; terrifying.
* Dire: extremely serious or urgent; desperate.
* Abominable: extremely unpleasant or repulsive.
* Fiendish: wicked and cruel; demonic.
Physical Descriptions:
* Flames: burning intensely; fiery.
* Scorching: extremely hot; burning.
* Sulphurous: smelling of sulfur; pungent.
* Stygian: dark and gloomy; like the river Styx in Greek mythology.
* Chasm: a deep, gaping hole or fissure.
* Abyss: a bottomless pit; a state of infinite despair.
* Cinder: a small piece of burning or partly burned wood or coal.
* Ashen: covered in or resembling ashes; gray.
* Boiling: very hot; bubbling.
Emotional Descriptions:
* Agony: extreme physical or mental suffering.
* Despair: the complete loss of hope.
* Anguish: extreme mental suffering.
* Desperation: a state of extreme urgency or distress.
* Dread: a feeling of great fear or apprehension.
* Loneliness: the state of being alone and isolated.
* Hatred: intense dislike or disgust.
* Fury: extreme anger.
* Regret: sadness and remorse for something done or left undone.
Metaphorical Descriptions:
* Hades: the underworld in Greek mythology.
* Tartarus: the deepest, darkest part of Hades.
* Sheol: the grave in Jewish tradition.
* Pit: a place of great suffering or danger.
* Deepest depths: the lowest point of something; a state of utter despair.
* A living hell: a situation of extreme suffering or hardship.
The specific words you choose will depend on the context and the intended effect.