History is littered with various secret and semi-secret cabals. Some more powerful than others and many have done serious harm in one way or another. Has any been all powerful? No thank the Lord, but not because they didn’t try. Like all such enterprises they have one weakness that is power sharing, no one wants to do it, so in the end there are always power struggles or outside powers who get worried, jealous and crush them.
The power I fear most right now is the growing power of the Islamifacist. Organizations that have form around religion have always been among the most powerful and when you combine that with the cult of death that Islam is it should be enough to make every sane man worry.