It is difficult to guess what the apocalypse will be if it certainly happens. We are more than once frightened by another "end of the world." But even if this happens, it is necessary to understand what scenario it will be. For example, many argue about the threat that will come from artificial intelligence (which has not yet been created). Well, or about anthropogenic catastrophe that will change the climate on earth and destroy large populations.

I will dwell on the technogenic catastrophe. If something terrible happened, the first thing people began to do is store food. Depending on the situation, vandalism would begin. People in a panic began to steal shops. The law would pass to the second plan. Survival is above all, and therefore those people who guarded the law went over to the other side.
Stocking food with the best varinat is to wait out a catastrophe somewhere in the shelter. This is logical because in life you will be more cautious.

State systems will cease to exist. Remain separate societies of privileged people who will have steep pieces with complete autonomy. To such people it is necessary to carry vyskikh officials and other people with authority. But their power on this and end as their monetary wealth will cease to have a key role. In fact, humanity will take a step back. It is unique to appear separate groups led by marginals (which in the modern world are highly primitive people).

Depending on the damage to be caused to the planet, individual people will look for solutions. I saw many talented people who know how to do unusual things from improvised materials. It is these clever people who will not be lost. And for ordinary people, life will be difficult. The food will end and this will be the main problem.

This scenario can be described in greater detail. But I see it as the mixture that was shown in the films "Mad Max" and "Book of Eli".