If you can build an AGI then a few billion autonomous exploding drones is no great difficulty.

That doesn't really follow.

AGI means you win the economy. Even if it's only John von Neumann level and not ASI (which removes the economy entirely), a version of von Neumann that can clone himself and never sleeps is surely capable of organizing an automated killer drone factory of sufficient size to remove as many humans as you like.

AGI just means that it can replace a human at any task - a single human. You still have compute as the bound on how many instances you can run, but even if those numbers are in the millions, the resources aren't going to magically come out of nowhere, either.

Half of them will vote to starve themselves so they can watch the other half starve, too.

I genuinely wish what you speak of happens should reality play out that way, but I think a lot of people will die with shit eating grins on their faces, even after they run out of shit to eat, because it means someone with blue hair is starving, too.