Ressentiment
Nietzsche's term for the reactive psychology of the powerless — the inversion of values by which weakness becomes virtue and strength becomes vice.
Ressentiment is a key concept of Friedrich Nietzsche's On the Genealogy of Morals (1887). Nietzsche borrows the French word to name the reactive emotional posture of those who, unable to act directly against their oppressors, accumulate a long-simmering hatred that eventually expresses itself in a moral revaluation: the values of the strong (nobility, vitality, spontaneity) are recoded as evil, while the conditions of the weak (humility, meekness, suffering) are recoded as good.
Nietzsche reads Christianity, and to a lesser extent democratic and socialist morality, as the historical product of slave revolt in morality — a long-form ressentiment that has reshaped European value over two millennia. The diagnosis has been enormously influential in twentieth-century social theory, from Max Scheler's phenomenological treatment to Frantz Fanon's analysis of colonial psychology. Critics charge that Nietzsche's account is psychologically reductive; defenders argue it identifies a real and recurring social-emotional structure.