Dawn of the God of War

Yu Geon is just a normal teenager, were it not for the fact that he's dying from a disease that gives him excruciating pain but also blesses him with supernatural strength. And despite his best efforts to focus on his illness and avoid the troublesome criminals and delinquents at his school, he has no choice but to intervene when their schemes cause a classmate to get kidnapped. Sick of their behavior, Geon decides to put an end to their crimes... even if it's the last thing he ever does.

(Source: Tapas, edited)