There are many theories as to who the harlot is:
Reading between the lines, I assume that the Harlot is a combination of Humanism and Spiritualism. She stands in direct opposition to God. She lusts for the things of this world: money, pleasure, luxury, pride, arrogance, and power. She thinks that she deserves it and has the right to obtain it even if she has to lie, cheat, steal, or murder to get it. The Bible is clear that those things are contrary to God. They are the essence of this fallen worldly system that is the Harlot:
1 John 2:15-16 (Berean Study Bible)"Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. 16 For all that is in the world—the desires of the flesh, the desires of the eyes, and the pride of life—is not from the Father but from the world.
Who is this harlot? We have looked at various ideas. Here is what I think it is: Humanism. The harlot represents mankind who exalt themselves and seek self-fulfillment. We see this more clearly in chapter 18. In that chapter, John describes all that is lost when Babylon is destroyed. This paints a very clear picture of the harlot:
That is why the harlot hates God and his people: They stand between her and achieving her desires. So, she persecutes the saints and kills them. It says she is drunk with the blood of the saints.
But the devil hates all mankind. Not just Christians. The harlot was just a useful tool. She led the masses into worldliness and sin. She used her influence to pave the way for the Antichrist to come to power. The devil totally hates those who follow Jesus. But he also hates the entire human race, including those who follow the harlot. They used the harlot to gain power. But once they achieved their goal, they turned on her and destroyed her.