An amorphous nickel boride/niobium carbide MXene (NixB/Nb2CTx) composite was designed and synthesized via a combined HF-assisted etching and in-situ chemical reduction strategy. The uniform anchoring of 0D NixB nanoparticles within the multilayered Nb2CTx nanosheets led to the formation of a robust composite with favorable interfacial interactions, abundant active sites, and improved charge transport pathways. The composite was directly coated on carbon cloth, which served as a flexible and conductive substrate to ensure efficient electron collection and mechanical stability of the electrode, while not contributing to electrochemical capacitance. Detailed structural and electrochemical analyses indicate that the integration of NixB with Nb2CTx influences the electronic environment, improves redox activity, and promotes ion diffusion, thereby contributing to enhanced charge storage kinetics. Among the as-prepared samples, the optimized NixB/Nb2CTx-50 electrode delivers a specific capacitance of 606.7 F g−1 at 1 A g−1, demonstrating a moderate rate capability with a capacitance retention of 43.2% from 1 to 20 A g−1. Furthermore, an asymmetric supercapacitor assembled with NixB/Nb2CTx-50 and reduced graphene oxide (rGO) electrodes achieved a remarkable energy density of 46.7 Wh kg−1 at a power density of 825 W kg−1. This work provides new insights into the interfacial engineering of amorphous transition metal boride-MXene hybrids toward next-generation high energy density supercapacitor applications.