Glioblastoma: This is the most common primary malignant brain tumor in adults, often presenting with a large mass effect, vasogenic edema, and symptoms related to increased intracranial pressure such as dizziness and altered balance. The location in the left frontal lobe and the significant mass effect with midline shift are consistent with this diagnosis.

Metastatic Brain Tumor: Given the presence of a large mass with significant edema and mass effect, a metastatic lesion from a primary cancer elsewhere in the body (e.g., lung, breast, melanoma) is a strong consideration. These tumors can present acutely and cause significant symptoms due to their rapid growth and surrounding edema.
Meningioma: Although typically benign, meningiomas can grow large enough to cause significant mass effect, edema, and symptoms similar to those described. Their location can be variable, including over the frontal lobe, and they can cause compression of adjacent brain structures.

Brain Abscess: Although less likely given the description, a brain abscess could present with a mass effect and surrounding edema. It is crucial to consider this diagnosis due to its potential for rapid deterioration and the need for urgent antibiotic treatment or surgical intervention.
Hemorrhagic Stroke: A hemorrhage within the brain could present with sudden onset of symptoms and significant mass effect. Differentiating between a hemorrhagic stroke and a tumor is critical for management, as the treatment approaches are vastly different.

Primary Central Nervous System Lymphoma (PCNSL): This is a rare form of non-Hodgkin lymphoma that can present with a brain mass, often with surrounding edema and mass effect. It is more common in immunocompromised patients but can occur in anyone.
Cerebral Toxoplasmosis: In immunocompromised patients, toxoplasmosis can reactivate and cause cerebral lesions that may mimic brain tumors. While rare in immunocompetent individuals, it's an important consideration in those with HIV/AIDS or on immunosuppressive therapy.