This study assesses the seismic susceptibility of a pre-existing reinforced concrete (RC) structure located in a high-seismic region of northeast India through finite element modeling. The study focuses on assessing the potential failure of columns to evaluate the building’ susceptibility to collapse. The building model was evaluated for seismic demands using Response Spectrum Analysis as per Indian Standards. A procedure is introduced to evaluate seismic demand and capacity of structural members for prioritizing strengthening. The building exhibited notable plan and stiffness irregularities, leading to its anticipated failure under seismic design conditions. For various load combinations, the demand-capacity ratio (DCR) for axial load and biaxial moments of columns was critical in evaluating safety. Results were validated by visual inspection of longitudinal cracks in columns under high combined demand. The six most critical columns were identified that could lead to collapse and need immediate strengthening. The feasibility of the approach as a tool for assessing the seismic performance of existing RC buildings and prioritizing retrofitting is demonstrated through this case study.