2D nanomaterials with atomic-scale thicknesses offer interesting properties in comparison with their 0D and 3D counterparts. Their ultrathin thicknesses signify quantum effects (electron confinement), which is responsible for unique electrical properties. Synthesis of highly conductive 2D nanomaterials has become an active area of research recently due to the high interest in miniaturization of electrical devices with improved performance and functionality. MXene--transition metal carbides, nitrides, and carbonitrides--has emerged owing to its unmatched electrical and mechanical properties. Polymer nanocomposites of polyvinyl alcohol (PVA)/Ti3C2Tx (MXene) are used for charge storage applications in the X-band frequency range (8.2-12.4 GHz). By implementing solution casting and vacuum assisted filtration (VAF) flexible thin-films with exceptional dielectric properties (solution casting @10.0 wt% MXene: ε'=370 ,tanδ=0.11 and VAF @10.0 wt% MXene: ε'=3165 ,tanδ=0.1) were fabricated. The reported dielectric constants in this study are the highest values obtained with low dielectric losses for polymer nanocomposites in X-band frequency. This outstanding performance originates from the high electrical conductivity of Ti3C2Tx MXene (≈1.4×10^6 S/m; highest reported value for Ti3C2Tx MXene over the literature), great dispersion state and the nacre-like structure of the polymer nanocomposites.