Bitterness occupies a distinctive and polyvalent position within the depth-psychological corpus, appearing simultaneously as a gustatory sensation, an alchemical principle, a spiritual pathology, and a psychological affect rooted in unresolved wounding. The most theoretically developed treatment derives from Jung’s extensive analysis of salt in Mysterium Coniunctionis, where bitterness — etymologically linked to the Latin mare (sea) via amaro — functions as the shadow side of wisdom: the two form what Edinger, following Jung, calls a ‘fateful alternative,’ such that where bitterness reigns, wisdom is absent, and vice versa. This polarity endows bitterness with a genuine transformative potential: it is not merely pathological residue but the raw material from which the salt of wisdom may be distilled. A contrasting clinical register appears in pastoral and biblical psychology (Shaw, Benda), where bitterness is traced to repeated rumination over injury — the re-opening of emotional wounds — and is understood as the foundation of resentment, rebellion, and spiritual corrosion. The ascetic tradition (Climacus, the Philokalia) extends this: bitterness is named as a ‘diabolical tree’ nourished by pride, whose eradication requires humility. Von Franz and Edinger amplify the alchemical-symbolic reading, associating bitterness with the Eros principle, tears, sorrow, and the wisdom acquired through feeling-experience. Across all these registers, bitterness marks a threshold condition — neither mere suffering nor achieved understanding — whose resolution determines the trajectory of psychological and spiritual development.