Cyberbullying

Not a single judiciary system is able to tackle a phenomena that can happens from anywhere in the world to anywhere in the world an can imply a handful of thousand of persons. Big tech does not have legal obligation nor financial or ideological interest to tackle it because forcing them would be unconstitutional. The rare cases where justice give a fuck about it, you get at best the condemnation of a bunch of nobodies after years of legal procedure during which the bully continues, and most of your bullies are still unpunished and free to launch a punitive expedition.

Impunity of members of UN security council

If a UN resolution is vetoed by at least one of the members of the UN security council, the said resolution is thrown in the trash. That means that if a war crime is serving the interests of at least one member of the UN security council, its full impunity is de facto guaranteed. Even worse: some of the members are notably war-thirsty and 2 of them aren't even democratic. And there is no way to change this way of functioning because it also can be vetoed by the said members. How many crimes have been made possible because of that?

Assholes.

Human nature. Itcwas necessary to beat out the other species, but it didn't evolve with society. Many of the things other people have mentioned are really just unevolved human nature. Greed, selfishness, racism, crime.

The limited scope of human attention and the ineptitude it creates in governance is impossible for a mortal being to fix in our finite existence. We will eventually formulate an AGI that can address this primal flaw, but defining who or what is fixing the issue becomes an unsolvable philosophical paradox in the idealized fantasy world of philosophical definition.