General Synonyms:
* Dismal
* Gloomy
* Bleak
* Downcast
* Dejected
* Disheartening
* Melancholy
* Morose
* Despondent
* Sombre
* Low
* Blue
More Intense Synonyms:
* Heartbreaking
* Soul-crushing
* Devastating
* Despairing
* Miserable
* Wretched
Synonyms with a Negative Connotation:
* Grim
* Oppressive
* Suffocating
* Stifling
* Heavy
* Burdening
Synonyms Focusing on the Feeling:
* Discouraged
* Hopeless
* Dispirited
* Despairing
Synonyms Focusing on the Situation:
* Tragic
* Catastrophic
* Unfortunate
* Dire
Synonyms with a More Poetic/Literary Feel:
* Rueful
* Mournful
* Lugubrious
* Doleful
The best synonym to use will depend on the specific context and the intensity of the feeling you want to convey.