This chapter examines toxic leadership in organizations, focusing on its causes, manifestations, and consequences for organizational health. The central aim is to deepen understanding of how toxic leadership escalates and undermines organizational effectiveness, achieved through a synthesis of long-term observations and experiences. The chapter draws on the author’s 30 years of professional experience as a participant-observer in the business world, enriched with auto-ethnography and critical case writing. Complementary methods include the analysis of approximately 100 cases of toxic leadership, 50 unstructured interviews with executives and professionals across various industries, and a meta-analysis of relevant literature. Data were analyzed using qualitative content techniques such as theme identification, open coding, descriptive coding, and pattern coding. Findings reveal that toxic leadership is characterized by behaviors such as instilling fear, eroding trust, micromanaging, and avoiding accountability. These practices exert severe effects on organizational culture, diminishing innovation, and eroding overall performance. Clear patterns emerged: declining quality standards, stagnation in organizational development, and the deterioration of relational ties. Toxic leadership poses one of the most serious threats to organizational health. Its persistent and systematic erosion of corporate culture reduces an organization’s capacity to leverage competitive potential and, in the long term, jeopardizes its survival in the marketplace. The chapter underscores the importance of a holistic response to toxic leadership, highlighting the necessity of promoting ethical leadership and implementing comprehensive organizational and cultural reforms. These findings carry significant implications for management practice, emphasizing the urgent need to cultivate compassionate, responsible leaders and to design systems that ensure long-term organizational resilience and sustainability.