My personal belief is that we will see catastrophic results from the use of AI by authoritarian governments or corporations long before we invent AIs capable of killing us; however, it is correct to view it as an X-risk. In a war against robots, we will lose. Why? Machines are stronger and faster than we are. Our only advantages are intellectual; but if we reach a technical level at which what we consider true intelligence is reduced to mere computation, then we have none. The distance between the first integrated circuit and an artificial human is massive (and we may never cross the chasm) but the distance between an artificial human and an artificial superhero/villain is not.

If we ever create a machine that's "as smart as" an average person, we're probably not very far from having one that's smarter than all of us put together. (Let's be honest; except in highly technical fields, the differences between a 150 IQ human's abilities and an average person's are not that great.) Should this happen, we'll soon enough be outmatched; we'll be just another animal in a world whose rules (ever changing) we cannot possibly understand... and just as humans have destroyed countless species often without conscious ill intent, it does not seem unreasonable that a robot successor would do the same to us.

Here's a thought experiment. Let's say we want to build not just a great Go player, but the best Go player that is possible in any world. Go is harmless, right? Sure, in isolation, but now let's imagine an AGI smarter than any of us which only "cares" about maximizing its Go proficiency. It's going to need a lot of energy. It'll hack or create robots and drill new oil wells (bypassing any constraints we put on it, since it in essence is spending thousands of human years figuring out how to escape). It'll devise nuclear technologies that may be unsafe from our perspective. Consider all the horrible things humans do in order to procure excess money (a commodity loosely correlated to energy) they don't actually need; there's no reason to think a badly aligned AI won't be just as inventive and horrible in its quest for more exajoules.

If capitalism and war are still the way of the world in 100 years, we are guaranteed to see some idiot inventing robot soldiers, hundreds of times faster and stronger than us, and with at least as much operational intelligence. He might never deploy the technology--a lab leak is in my opinion more likely--but at some point, it will get out. It won't be one robot; it won't have a body we can destroy. It'll be able to replicate itself and beam copies to satellites. It'll have control of our power infrastructure (which it will divert to its own "wants") within hours. We'll be screwed, not because it will want to harm us, because our lives require the use of resources that it will divert toward some objective function we technically invented but do not understand.