The issue of toxic leadership, marginalization, and favoritism-(nepotism-cronyism) one of the important issues that represent risky phenomena and real problem that impact and results in many negative effects on the sustainability of human capital. But the question remains, which of these managerial and psychological variables affects the sustainability of human capital most? Is toxic leadership or marginalization or favoritism or ergonomics or servant leadership are the most or least impact on the sustainability of human capital? The research focused on a puzzling subject in managerial thought philosophy and studied six variables: toxic leadership, marginalization, favouritism- (nepotism-cronyism), ergonomics, and servant leadership and their impact on the sustainability of human capital. a sample of (371) Cairo international airport (CIA) employees. Finally, the study measured and determined the six most important variables that impacted the sustainability of human capital and tested the ten research hypotheses. Additionally, suggested some recommendations and implementation mechanisms that raise the efficiency of the airline sector and contribute to moderating the effects of toxic leadership, favoritism-(nepotism-cronyism) (FNC), and marginalization on employee performance and enhancing the role of servant leadership (SL), providing and improving ergonomics (workplace conditions and environment), which contributes to the sustainability of human capital (SHC).