Soil contamination with heavy metals presents a significant threat to environmental and human health. Traditional remediation approaches are often cost-prohibitive or ecologically disruptive. This review explores sustainable, low-cost techniques, specifically focusing on the comparative efficacy of biochar and Delonix regia pod powder in immobilizing heavy metals in tropical soils. Drawing from both laboratory results and contemporary studies, we evaluate key factors affecting remediation efficiency, including soil pH, organic matter, contaminant concentration, and treatment aging. Biochar emerges as a robust amendment suitable for a wide range of contamination levels and soil types, while Delonix regia pod powder demonstrates promise in nutrient-rich agricultural settings. Emerging insights, limitations, and future directions are also discussed.