Exactly! In this world, if the man dies, he will not face justice in the hands of men. Islam tell us, justice, the ultimate justice will be executed in the life after death. One can choose to believe this or not believe this. That's a matter of choice.
I get your reasoning completely and it's very human but I have something to interject... What is justice? Every single culture has its own form of understanding of justice and they create their own systems to try and implement that form of justice. For example, Islam tries to tackle thievery by chopping off hands. Now, a secularist would deem that to be immoral because it reflects the value system of an ancient world that we no longer agree with. A Muslim would argue that it works (that is highly debatable of course) and that what comes from God is always just (special pleading at its finest).
Imagine the first human beings in there small little communities that they've established to secure their survival...they've realised at some point (probably due to instability) that they must set up some sort of system to ensure stability. This is where our current perceptions of morals derived from. A set of laws and systems had to be created to ensure order and stability. (I also believe that this has a lot to do with the rise of religion but that would be detailing). This is evident from the fact that every culture has its own understanding of what is right and what is wrong. Also, morals change.
Now, in my opinion, your entire reasoning for a hell seems to derive from the evolutionary urge to see evil people punished. To me, you made an emotional argument rather than an actual one based on reason and facts. We have no evidence for the existence of an afterlife where bad people burn for eternity.
I disagree that men like Stalin have got away with their punishments. Suppose he was buried, do you know what happens to his ashes? They return into the Earth that it came from. Do you know what happens after that? The ashes are then "recycled" by nature and used to create some new and magestic creature. It's very beautiful in my opinion.
Moreover, Muslims have used the Quran to commit heinous things that I believe everyone, including Muslims, would regard as immoral. Chopping off hands, jizya, slaveri and sexual slavery and etc.