Context:
Agile software development (ASD) methodologies address problems of traditional approaches, but can also cause various issues. A systematization of the spectrum of negative facets and how they arise has not been developed, leaving the dark side of ASD opaque.

Objective:
The paper systematizes findings on various negative facets to define what specific issues constitute the dark side of ASD. It also examines how relationships among these issues define the complexity of the downside.

Method:
A literature review of 70 articles was conducted following Kitchenham & Charters (2007). The content analysis employed the coding procedure by Gioia et al. (2013) to systematize the negative aspects of ASD methodologies.

Results:
The paper reveals 90 issues, grouped into 18 coherent themes. Six levels of manifestation point to the primarily affected constituents in ASD projects. In addition, 65 relationships among issues are explored, providing explanations for the complexity of the dark side of ASD.

Conclusion:
The systematization shows what aspects constitute the dark side of ASD, emphasizing its multidimensional nature along issues such as reduced developer well-being, product quality and development productivity. The analysis of how its complexity is defined reveals that customer misbehavior and delivery pressure are significant origins of other issues.