AI, the next step with possibly the biggest risk. Many if not most people are afraid of AI. Many movies depict Ai as the prime enemy of humanity, ex.(I robot, matrix, bladerunner, and terminator). The reality of the situation is Ai will befriend humanity or at least not harm it.
Unless the fear of a small idiotic group of people go and attack AI, creating a reaction. Creating the same reaction they feared would happen by not attacking. This would become the stuff you hear of in legends and myths, a self-fulfilling prophecy. By lashing out to prevent an attack, they cause an attack wiping out humanity.
However the issue with AI is that they are too fragile.The possibilities with AI however, may outway the problems. AI cars have already arrived. You most likely use AI everyday, whether it is, siri or internet searches. But those are examples of weak AI, strong AI on the other hand could outperform humans in nearly every mental task according to future of life. There are many years though before strong AI would become a reality. Hopefully by then we will have an alternate solution to tackle the possibilities, some options are to start an underground or  deep sea colony. Another interesting idea is to start a space colony of AI.
AI most likely will not attack unless we interfere with their goals.  And if you think AI don’t have goals then,”a heat seeking missile has a goal”(future of life). So to avoid interfering with their goals we must make AI’s goals aligned with ours. For example, AI is a river slowly making its way over to a small village, the village is humanity. You cannot simply put a wall up to stop the river for it would eventually fall. You must redirect the river so it does not harm humanity. Of course this example is flawed but, I hope it helps you get the point.
Overall AI may not become a reality at all, but if it does we hopefully will be prepared, and laws will be in place. So we all stay safe.