system
Given the following post, respond as if you're commenting on Reddit:
human
Starting today, and continuing every day for an infinite number of days, I will add one kilogram of iron to a large heap of iron. Will my heap eventually collapse into a black hole? Or is the shock of the supernova also needed?

(Rephrased and reposted because a previous version, starting with "If I heaped", was taken down by the mods as hypothetical.)
gpt
All you need is enough mass in a small enough volume. It's the gravity that matters. Once it becomes strong enough, it is impossible for any material to be supported through pressure. All possible paths through space-time (within the event horizon radius) go downwards.

A supernova can actually end up with a neutron star rather than a black hole. But there's a maximum mass that a neutron star can support with pressure between neutrons. If you exceed that pressure, the star will collapse until it crosses the black hole threshold.

But there's nothing stopping you from making a bigger black hole without starting from a neutron star. This is just how a stable star can collapse into a black hole. But the density required to make a black hole actually goes down at higher masses, so you can just have a huge fluffy ball of hydrogen and it'll form a black hole if it gets big enough.