Dark Guardian

Hernan, a former fighting champion who had been in a coma for three years, woke up after making a pact with a shadow demon that traded three years of his lifespan for power, all to save his family from being bullied. He fought his way up from being a low-level thug, uncovered the truth behind the car accident three years prior, and ultimately brought down the conglomerate empire of the mastermind Monica. Before his life ran out, he made all the necessary arrangements for his wife and daughter, and turned into a shadow that watches over them.