An excellent late-game strategy I have found is abusing the UN. The key is to aim for mass media and build the UN as quick as possible. Once you control the UN you should be able to get yourself elected as Secretary-General every time. Also, I recommend you have some friends or a few vassals, either will work. Just as long as you (and your friends/minions) control 51% of the population. Now, every few turns or so the game asks you to propose a world-wide resolution. The key is to pick one you know will be defied. The easiest is asking for the world-wide adoption of "secular" because the AI always clings to its religions. The resolution will appear to fail, even though you received the majority of the votes in favor. This is because the AI defied the resolution. This is the goal, because when they defy resolutions all their cities get a +5, "The world considers you a villain." Every time you can choose a resolution make sure you choose an unpopular one so they add up. This is the key because the AI cities will quickly go into disorder after 3 or so of the failed resolutions as the +5 are cumulative. Now, all of the dissenting AI will have their own revolutions to deal with while you mop the floor with them. Who ever said the UN was useless?