<p>The increasing need for sustainable solutions to environmental pollution has highlighted the importance of sorbent materials, particularly activated carbon, in removing a wide range of contaminants, including heavy metals, organic pollutants, and dyes, from aqueous and gaseous environments. This review provides a comprehensive assessment of the role of activated carbon in environmental remediation, with a focus on key factors influencing sorption efficiency, such as precursor chemistry, activation methods, and sorption mechanisms. It further discusses carbonization and activation strategies including physical and chemical methods, as well as one-step and two-step processes in relation to pore development, surface area, and functionalization. The sorption mechanisms of heavy metals, including electrostatic interactions, ion exchange, surface complexation, and pore diffusion, are analyzed together with performance metrics for individual and multi-metal systems, regeneration potential, with comparative evaluation against commercial carbons, and emphasizing the roles of precursor selection and activation conditions. Also, the review addresses the environmental implication and sustainability considerations, including waste valorization, energy and chemical efficiency, life-cycle impacts, and circular economy integration. The challenges, knowledge gaps, and future perspectives are also outlined, suggesting guidance for the rational design, optimization, and practical application of agricultural waste-derived activated carbons for efficient, sustainable, and scalable heavy metal remediation.</p>