Background: Patients with advanced lung malignancy are vulnerable to disastrous pulmonary complications, especially when structural tumor necrosis, infections, and critical illness intersect. Bronchopleural fistula (BPF), persistent pneumothorax, and invasive fungal infection are rare but often fatal. Case Presentation: We report a 60-year-old man with recently diagnosed lung adenocarcinoma who presented with acute hypercapnic respiratory failure, hypertensive crisis, and severe leukocytosis. Initial imaging revealed diffuse multifocal pneumonia. Despite starting non-invasive ventilation, he required intubation, which was complicated by a large right-sided tension pneumothorax and persistent air leak requiring chest tube placement. His hospital course rapidly deteriorated with the development of diabetic ketoacidosis (DKA), septic shock from Clostridium perfringens bacteremia, progressive acute kidney injury (AKI), and extensive cavitating lung destruction with BPF. Serial imaging showed worsening cavitation, suspicious for necrotic malignancy rather than superimposed infection. Bronchoalveolar lavage (BAL) grew invasive pulmonary aspergillosis (IPA). Surgical and endobronchial interventions were not viable due to extensive disease and critical illness. Despite aggressive antimicrobial and antifungal therapy, the patient developed massive hemoptysis leading to pulseless electrical activity (PEA) arrest and death. Conclusion: This case illustrates a lethal cascade of cavitating lung malignancy complicated by BPF, polymicrobial sepsis, and invasive. Early recognition of structural lung compromise and prompt multidisciplinary discussions, including goals of care, are essential in critically ill patients with advanced pulmonary malignancy.