Who are the 4 autocratic leaders of the world?

Autocracy (unbounded and unlimited rule of one person) and politics (the sets of mechanisms and rules by which policies are built, applied and enforced) are incompatible, if you take the narrowest meaning of the terms.

Moreover, some researchers, especially those quite distant from political theory (and mainly working in international relations) use autocracy as a short-hand for "lack of democracy", which others consider as a grave mistake (the proper term being "authoritarian regime", out of which autocracies are just a subclass).

This would be a list of autocratic rulers in the most narrow sense of the Word (having discretionary, unbound power without control from either rules, institutions or ideology) : The czars of Russia (from about Peter I'st proclamation as Emperor in 1721 to Nicholas II in 1917) , the rulers of Saudi Arabia (up to and including Abdullah bin Abdul Aziz, the current king), some other rulers around the Middle East (in, for example the Emirates or Kuwait) some sultanistic yet not truly totalitarian rulers (such as Uganda's Idi Amin in the 70s, Iraq's Saddam throughout the 80s and 90s, Romania's Ceausescu in the 70s and 80s etc.). A closely linked regime-type to autocratic regimes are totalitarian regimes. However, those are, for many theorists, not autocratic, as their rulers are bound by a totalizing ideology, and cannot act truly discretionary.

In the wider understanding of the term, all non-democratic states are "autocratic" (including truly autocratic, totalitarian, authoritarian, military-led etc.).