Sustainable development requires not only knowledge and competences but also specific attitudes that arise from distinct forms of awareness. Critical thinking, self-reflection, and empathy encapsulate various but interconnected aspects of the education essential for achieving sustainable educational objectives. This article primarily examines the role and significance of critical reflection in cultivating competence building in sustainable development. Its aims include assessing the current state and comprehension of criticality within didactic processes in this domain. Special emphasis is placed on the power dynamics underlying the context of the discussions and the very understanding of critical thinking. The analysis also encompasses the actual and potential impacts of the rapid advancement of Large Language Models on competence-building processes, as well as the cultural diversity in critical perceptions of sustainability itself. We illustrate this approach with practical examples drawn from a significant teaching experience within the Widening Interdisciplinary Sustainability Education project. Key findings of the chapter include highlighting the necessity of adopting a critical approach to any understanding of sustainability that aspires to be culturally, cognitively, and politically sustainable, while also outlining a framework for a sustainable education model that integrates critical thinking.