Rise of the Sun God

Before he rose to power, the signs of his evil genius were present. Only a few noticed.

Seemingly ordinary parents give birth to a boy with god-like powers—and soon discover that his magic is matched only by his propensity for evil. When the boy's mysterious grandmother appears and takes him away to a distant place, the parents are filled with relief.
But the boy named Invictus does not like taking orders from anyone. Very quickly, even his grandmother—a demon in disguise—cannot control him.
Eventually, Invictus learns that he has a younger sister, purposely hidden from him—but hidden no longer. And so he returns to his birthplace, obsessed with winning her over . . . no matter what.