This research investigates the effects of crystalline (chamotte), amorphous (nano-clay), and functionalized particulate additives on the performance of metakaolin-based geopolymer (MK-GP) composites under diverse curing protocols, including temperatures of 21 °C and 150 °C and pressures of 0.1 MPa and 40 MPa. Key performance metrics—flexural and compressive strength, porosity, and thermal stability—were evaluated alongside microstructural evolution analyzed via Environment Scanning Electron Microscopy (ESEM). Results indicate that all additives improved geopolymer performance, with chamotte acting as a filler and dehydration regulator, nano-clay providing an additional aluminosilicate source, and carbon nanotubes modifying setting behavior. Each additive reduced pore size, enhancing the composite's properties. The hybrid combination of additives showed a synergistic effect, significantly enhancing compressive and flexural strength, with improvements of up to 350 % compared to plain geopolymers under similar curing conditions. Additionally, the mechanical performance was minimally affected under high pressure (40 MPa), emphasizing the potential of hybrid reinforcements for extreme environments. These findings highlight the critical role of optimizing particle size, composition, and chemical compatibility to develop high-performance geopolymer composites for challenging applications.