Demon King's Good Karma System

The strongest being in the world, even gods were vary of, the demon lord had killed all his opponents. He was the supreme with unparalleled strength and supreme powers, he could not be defeated. Looking down even at gods, he was not afraid of anyone. But who would have thought that he would be backstabbed by his own family.
Killed by his own brother, he decided to take revenge if he would get an extra chance. But when he opened his eyes again, he was on earth not in his world of demons and that also with a shitty “GOOD KARMA SYSTEM” that could only let him live if he would collect sufficient points by the end of the day.
To earn the points, he had to do good deeds, and so his struggle to gain the points began. The man who had only cared about himself and only killed people like they were insects had to struggle and beg to help others so that he could get his long awaited revenge.
But after doing so much goodness, would his system let him kill his killer for which he had come back to life and struggled so much?