Ion-electron-coupled interfacial reactivities on electroactive particles are complex and crucial to various battery chemistries and dynamics, yet direct in-situ reactivity visualization remains missing despite advances in operando imaging. We report ion-localization optical nanoscopy (ION) with single-ion, subparticle resolution that distinguishes microscopic static and dynamic disorder in ion-generation interfacial reactivity, offering nondestructive, real-time, nonequilibrium insights. We uncover diverse stripping dynamics of zinc anodes, revealing unexpected subparticle-position dependencies and challenging conventional views of uniform stripping on (002)-textured zinc. New mesoscale functional descriptors–intraparticle diffusive and electronic coupling strengths–that govern overall stripping uniformity are identified by ION, supported by computational methods and validated by in-situ single-particle manipulation. Imaging-derived insights are further translated into ensemble-level strategies that enhance macroscopic performance, achieving exceptional anode reversibility. ION is cost-effective, high throughput, and broadly applicable to myriad ion-participated interfacial processes, including cathode (de)intercalation, solid-electrolyte-interface (SEI) evolution, ion exchange, and catalyst restructuring.