State-led mass violence against civilian populations remains a pressing global threat, yet the international community is often caught off guard when such events occur. Dominant structural and strategic explanations overlook key psychological factors contributing to leaders’ violent decisions. Drawing on theories and methods from political psychology, cognitive anthropology, and terrorism risk assessment, this study introduces a novel framework linking psychological traits detectable in leaders’ language to patterns of mass violence. We compiled a database of over 700,000 words from twenty authoritarian leaders of the past 120 years. Combining expert assessments with natural language processing, we examined associations between psycholinguistic clusters and levels of lethality. Our pre-registered analysis identified distinct psycholinguistic profiles, each linked to different levels of lethality. These findings provide initial evidence that linguistic indicators of leader psychology can help explain variations in state-led violence. Our theoretically-grounded framework may contribute to the refinement of early-warning and risk assessment systems.