In the past, single human brains have come close to destroying the world, and lots of people have access to supercomputers, so the barrier doesn't seem insurmou

In the past, single human brains have come close to destroying the world, and lots of people have access to supercomputers, so the barrier doesn't seem insurmountable. I don't think you need AGI to cause a catastrophe. A narrow AI specializing in cyberattacks could be catastrophic, and is probably possible with current techniques.