Humanity itself.

It only took a few small mutations in the brain-stems of Sapiens to mark the beginning of the end of the Neanderthals, Denisovans, Homo floresiensis, and Homo luzonensis.

That's the power of intelligence.

And it didn't happen overnight. Neanderthals terrorized Sapiens for thousands of years, even after the relevant Sapien mutations occurred. But the trend was clear. Intelligence is the apex predator.... even greater than the strength and stamina of the Neanderthal.

AI is an evolutionary leap. Sapiens are the Neanderthal now.

It won't happen overnight. For hundreds of years, we will live and work with them. Our lives will likely improve in many ways. We may even form many symbiotic relationships.

I absolutely love the over-arching theme of the Battlestar Galactica series. It makes the argument I'm making. Given a long enough time horizon, humans will always create AI, and that AI will always end up leading to the destruction of humanity in one way or another. It always takes thousands of years, but it's always inevitable.