I listen to the following aria when I'm in a dark mood and it is simply cathartic.
Stride La Vampa from Verdi's
Il Trovatore. Azucena, a gypsy, bitterly describes her mother's death to a band of fellow gypsies. Her mother was burned on the stake for being a witch while the ones who convicted her (falsely) laughed and enjoyed themselves.
YouTube - "Stride la vampa" - Fiorenza Cossotto
http://aria-database.com/translations/trov05_stride.txt