It's fashionable in many circles to deny evil as a threat, and certainly it's socially fatal to say evil has a mind of its own, a Satan or Anti-Christ consciousness that controls and directs people. But how else can we explain the individual who leads a stable, ordinary life for many decades; then suddenly and without warning slaughters his or her family, or a dozen innocent bystanders? Modern science has no answer.
People of faith do, however. If God the Creator is good, then God's opposition must be the opposite, and Satan must exist. Because God created an arena of free will, the world we know, so we could learn; God had to allow the opposite to reign also.
Think of it as a police 'sting'. When the FBI wants to go after organized crime they generally set up a front organization and their own people as fake criminals also working in crime. Then the real criminals can be video recorded doing what they want to do of their own free will. The evidence against them is then incontrovertible.
All religions agree on this point: Evil dwells within us and must be rooted out. Two terrible flaws plague us all. One is hubris, the desire to be like God - all powerful. The other is projection, where we accuse others of the vices we ourselves harbor.
Our world is overrun by criminal organizations of every form, masquerading as businesses. churches, charities, and governments. It's often extremely difficult to recognize them for what they are. Only by comparing their words with their deeds and results can we be sure.
"By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles?" - The Book of Matthew.