This study investigates the enhancement of punching shear resistance in reinforced concrete (RC) flat slabs. It explores the use of circular holes filled with Engineered Cementitious Composites (ECC). Within each drilled ECC hole, one of four strengthening configurations was embedded. These configurations were: Glass Fiber-Reinforced Polymer (GFRP) textile wrap, welded-steel mesh (WSM), steel bolts, and post-tensioned steel bars. This study aimed to permit a direct performance comparison under identical slab geometry and loading conditions. Despite the many studies on strengthening the punching of RC slabs, there is no study assessing ECC-filled drilled holes, implementing active prestress via post-tensioned bars inside ECC, and comparing four distinct strengthening strategies in such a configuration. The research evaluates the impact of these techniques on crack initiation, load capacity, and failure modes, demonstrating significant improvements in slab performance. The effectiveness of a novel pre-tensioning system is also assessed, showing promising results in increasing the slabs’ load-bearing capacity and energy absorption. Slabs strengthened with post-tensioned steel bars emerged as the clear outperformers as they exhibited a remarkable improvement in both crack resistance and overall load capacity. They displayed an impressive increase of over 50 % in the load at which cracks first appeared, and a staggering increase of over 55 % in the maximum load they could withstand. These benefits extended beyond ultimate strength, as the post-tensioned slabs also demonstrated a significant increase in stiffness.