<p>Most landslide hazard assessments remain confined to a single spatial scale and therefore fail to reflect the integrated regional and local processes that govern slope behavior. This study presents an integrated slope-safety assessment framework that unifies catchment-scale statistical susceptibility analysis, site-scale physical modeling, and advanced reliability evaluation, applied to the Zhuoshui River Basin and the Wanda landslide. While frequency-ratio mapping identifies basin-scale hotspots, it cannot resolve mechanical response or progressive deformation. This study incorporates long-term creep into the expected slope displacement loss (<i>EL</i>) formulation, acknowledging that cumulative post-failure deformation is an alternative measure of slope impact than binary stability. The Material Point Method (MPM) is employed to simulate progressive large deformation in a mechanically consistent manner under varying groundwater conditions. The in-house AK-PSO-HHs algorithm enables efficient and accurate failure-probability estimation, overcoming the otherwise prohibitive computational demands of reliability analysis for advanced large-deformation simulations. By integrating susceptibility mapping, MPM simulation, and uncertainty quantification, the updated standardized CDF of the Landslide Susceptibility Index provides a robust basis for <i>EL</i>-based protection planning. Results indicate a slow-creep, self-adjusting slope behavior in which the slope repeatedly attains new equilibrium states, and that infrastructure in the Wanda area should be planned to accommodate about 10.22 m of cumulative displacement. This work is presented as a demonstrative application of an integrated assessment workflow rather than as a generalized methodological paradigm, providing a rigorous and scalable reference with clear practical applicability for comprehensive slope-safety assessment.</p>