When I was a child, I used to think as a child. I thought of true evil as a cartoon villain who couldn’t love, trying to destroy the world merely to destroy it: That Evil must be in direct opposite of Good; destroying for the sake of destroying; killing for the sake of killing. That to destroy with strewed intentions of doing good has a shred of innocence, and is not truly evil.
It was St. Augustine, though, that once said that evil is really a ‘disordered love’; That it’s not so much the opposite of Good, but the corruption of it. Like Cancer cells to healthy cells of our souls, evil is the Good in our lives twisted to wrong meastures.— When God created the world, he called it good; When he created Man, he called it very good.— The true human nature is good, perfect; but evil is the corruption of our nature, like a lie is the corruption of Truth, or cancer is the corruption of the body.
One of the most maturing thoughts I ever had was realizing the Tyrant that kills millions doesn’t actually say in his heart "I’m evil and I enjoy it," but honestly "I’m making the world a better place." For even Hitler thought he was acting 'for the good of all humanity.'
Augustine illustrated the battle of Good Vs. Evil not as two opposite forces ever-warring with equal arms over the fate of the World, but as this: It is that of two cities together; ‘The Eternal City’, the City of God, that stands for Good. But the other— it is not the City of Hell, or Sin but the ‘City of the World’, that along with God, stand’s for the Good, but is under siege, and occupied territory by what is Evil, like a cancer invading our body. And all of God’s and man’s struggle together is to reunite these two cities, and restore everything back to the Good.