Purpose
Throughout history and in modern times, leaders with a "dark side" have emerged across various domains, such as politics and economics. To address the issue of effectively managing such leaders, we developed a scale of dark side Leaders. This scale aims to measure personality traits often associated with workplace bullying and harassment—such as the Dark Triad traits (Narcissism, Machiavellianism, and Psychopathy), Extreme egocentrism, and Sadism—while emphasizing leadership perspectives. Hypothetically, this scale was assumed to relate some of the Dark Triad and Big Five personality traits.


Method
In this study, the Dark Side Personality Leader Scale (DSPLS) was developed, comprising 20 items representing five factors (Narcissism, Machiavellianism, Psychopathy, Extreme egocentrism, and Sadistic leadership). The total of 1,988 participants (mean age = 51, SD = 15) completed an internet-based questionnaire. The collected data were analyzed using confirmatory factor analysis (CFA).


Results
The results supported a five-factor model, demonstrating a good model fit to the data (CFI = .949, TLI = .939, RMSEA = .066, 90% CI = [.063, .069]). The Cronbach's alpha coefficients for each factor in the DSPLS ranged from .72 to .92. Furthermore, the scale achieved an optimal score in the Mokken Scale Analysis (Ht ≥ .42). The DSPLS score showed significant positive correlations with the Dark Triad Dirty Dozen traits (Jonason & Webster, 2010). Additionally, it exhibited significant negative correlations with agreeableness as measured by the TIPI-J (Gosling et al., 2008).


Discussion
The DSPLS was validated against the Dark Triad scale, confirming its hypothesis and validity through a negative correlation with agreeableness in the Big Five Personality. Leaders with dark personality traits, marked by low empathy, likely exhibit weaker cooperativeness. Future research will explore links between leadership styles and workplace harassment.