A man with a knife intent on doing harm, is stopped by one with a gun.
A man who develops a virus for a plague to kill people, is stopped by one who develops the cure.
A man who develops icbms to devastate a nation, is stopped by one intent to develop a missile defence shield.
There are many examples that I could continue with. The key takeaway here is that whatever some one does, in time there is an equal opposite reaction to counter it.
That's my world view. I personally don't fear anything. But then that's could be just how I'm built.