Context. The characteristics of software professionals have been widely investigated in the literature. However, limited attention has been given to undesirable attributes in Requirements Engineering, despite the strong dependence of this activity on stakeholder interaction and collaboration. Objectives. This study investigates the undesirable attributes of requirements engineers' hat may hinder collaboration and project success. Method. We surveyed software practitioners to identify these attributes and conducted interviews to gather supporting evidence. Results. Seventeen undesirable attributes were identified, grouped into four categories (communication issues, lack of domain knowledge, personality, and lack of technical knowledge), and organized into conceptual maps. Conclusion. The maps help requirements engineers reflect on and improve their professional practice by recognizing traits that may hinder collaboration and project outcomes.