An erosive jet can propel degradable, abrasive grit conveyed in a carrier fluid to erode a downhole structure, such as a tubular (e.g., cutting through a tubular) or formation (e.g., perforation actions). The abrasive grit can be selected to degrade or dissolve in the wellbore fluid (e.g., in carrier fluid pumped into the wellbore or in fluid originating from the wellbore). The abrasive grit can provide increased cutting or erosion efficiency in the erosive jet during the cutting operation, then may degrade (e.g., dissolve) in the wellbore fluid to avoid certain complications, such as clogging or residue build-up in the wellbore formation or on downhole equipment. A degradation accelerator can be introduced (e.g., in carrier fluid) to accelerate degradation of the abrasive grit in the wellbore fluid. Degradation accelerators can be temperature-activated, pH-activated, or otherwise time-delayed so the abrasive grit remains sufficiently intact to perform the desired erosion operation.