The villain with the system (Hero Killer x male reader)

The world is in constant turmoil, with constant wars breaking out between Heroes and Villains. Gifted with supernatural abilities, one lone girl sets out on a bloody path for revenge against the injustices of the world she lives in. With the constant clashes between titans, no one is safe. If no one is willing to protect the innocent, who are the real heroes, and who are the real villains? What truly separates one from the other. But what that lone girl dones't know, is that she won't be alone for much longer, as another shadow will rise to kill heroes.