China. This is obvious, and much discussed.
Islam. It cannot coexist with Western Civ, or any other religion. We are seeing that in Europe today. Countries that allow Islamic immigrants eventually turn Islamic and backward.
Africa. The UN projects that African population will explode for the foreseeable future. In a century, there will be billions of Africans, and they will overflow to all the other continents.
AI overlords. In a few years, AI bots will be running the world. I think that they can be tamed, but time will tell.
Reptilian shape-shifters. I know this theory is wacky, but it predicts much of the social subversion we see today. Some of it is associated with Jews, but that is a distraction, as Orthodoc Jews are not in on the plan.
World War III. I was not worried about it, until the reckless warmongering of the Biden administration. Escalating the Ukraine War is dangerous.
Wealthy robber barons. Economists commonly predict that GNP will continue to grow at 2% or more for the next century. If so, there will be enough wealth for everyone on Earth to be rich. No one knows how to manage that much wealth. It seems much more likely that a small minority, less than 1%, will control all the wealth. Everyone else will have opportunities to be comfortable, but they will hate the super-wealthy.
If I had to guess, I might predict that the reptilian shape-shifters will exterminate the Moslems and Africans, leaving the world for the Chinese, AI bots, and robber barons.