A 52-year-old man from Mumbai presents with a 3-month history of progressive weakness in the right arm and leg, followed by generalized tonic-clonic seizures. MRI brain shows a large, ring-enhancing mass in the left motor cortex with significant vasogenic edema and mass effect. The lesion demonstrates high signal on diffusion-weighted imaging (DWI). Histology shows a highly cellular neoplasm with marked nuclear pleomorphism, numerous mitotic figures (>10 per 10 HPF), and areas of necrosis surrounded by pseudopalisading cells. GFAP and p53 immunostains are strongly positive. IDH1 R132H is negative. What is the most likely diagnosis?