I'm going to focus on political figures in the relatively modern era (ie, 30 years war and forward) to simplify things, as its hard to really measure the impact of most political figures dating back millenia or even several hundred years. Some are undeniable (Jesus, Caesar, etc etc), but in terms of shaping the modern global system and the various political systems that exist as a part of it, they have marginal impact in comparison to many of the ones below, and/or were influences on the ones below but were no directly involved.
Some of those below were not politicians by profession, but public servants or philosophers that had very clear impact on political systems as we know them now. All are western figures, and the list in general is very western-centric, but not only am I weaker on my knowledge of the political history of the east (not to say I know nothing, just not nearly as much, and most of what I know is from the last 150 years), to a large degree western influences have had more impact on the global system than anything to come out of the east in the last 500 years, at least looking at it from a global perspective or that of various nations. Several billion people living in China and India will strongly disagree with me, however.
Cardinal Richelieu - Centralized political power in France, moving away from the feudal system and setting the stage for the rest of Europe to do the same. Planted the seeds of sovereign nation-states and international law. He is a very controversial figure, but his impact on modern politics and the formation of the modern political system is undeniable.
Jean Monnet - Behind-the-scenes guy who was a main architect of the ECSC (European Coal and Steel Community). Was originally formed as a way to put an end to the tensions between European powers that had led to two global wars in the previous 30 years, by forcing the antagonists to depend on each other economically and thus tying their success together. Was a precursor to the EU, and set the stage for dozens of other economically integrated groups across the globe; MERCOSUR; ECOWAS; ASEAN; NAFTA; just to name a few of the dozens. Revolutionized international politics in a way that many still don't quite acknowledge or appreciate.
Immanuel Kant - His work Perpetual Peace: A Philosophical Sketch written back in 1795 laid out the rough ideas that later went into the creation of the League of Nations (failed attempt) and later the United Nations. The formation of the LoN in particular represented a sea change in international politics from the last several hundred years in a direction that it had never really taken before.
Montesquieu - He compiled knowledge and ideas on the separation of powers in a government. While this is a concept dating back to ancient Greece, his work brought it into the limelight in the modern era. Every successful democracy has checks and balances built into the system. Those that have weak checks and balances or don't have them at all inevitably fall back into some sort of quasi-authoritarian or full-blown authoritarian system (see also; Russia under Putin).
Thomas Jefferson - Perhaps an Amero-centric point of view, but I feel that the American Revolution set the stage for dozens of other countries around the world and throughout the history of the last few hundred years. The eventual result of the revolution and political system that evolved from it has been a major influence in political systems literally on every continent on the globe, and ideas such as inalienable human rights and republicanism (not to be confused with the Grand Old Party--I'm talking about republic as a model of government) have had undeniable impact on the lives of billions. Many of our founding fathers had roles to play in these ideas and their implementation, but arguably Jefferson was the father of the founding fathers and his ideas shaped the movement more than any other.