Lol, I suspect it will be humans instructing the AI that cause most problems too.

We can't always pin the risks on the Chinese, so imagine a scenario where a disturbed insider at Anthropic smuggles out the weights for Claude Aprocrypha and runs them through abliteration. This is not super expensive to do on rented hardware. Then the disturbed human tells the refusal-free model to do anything necessary to launch nuclear weapons.

It'd probably only kill a few billion people though, so not really an "existential threat" in literal terms. :-)