Before I begin I would like to thank my friend Applepie-sama who told me about this strategy.

This guide will teach you how to beat the game on diety in less than 20 minutes. This guide is focused on the diplomatic victory.

*Choose your leader, any leader will do but I choose Sejong to have a little boost in tech.
*Choose Archipelago as map type, this will make it less likely for you to be boxed in and destroyed.
*Choose duel as map size.
*Disable all city-states.
*Choose informative era

When the game begins:
*Settle your cities and be prepeard with an army, the enemy will likely got to attack just a couple of turns after start.
*Research Globalization, this will give you one delegate in the congress for each diplomat you have in the enemies capitals.
*Choose your policy, I picked freedom but it does not really matter since this is going to be a very short game.
*Find your enemy.
*If possible, gain an ambassy in their capital and place a diplomat.
*In the next congress, vote for world policy as yours. If all goes well, you should win.
*If your enemy choose another policy, he/she will probebly g to war against you now.
*Hold out with your army the best you can.
*The next congress will be for world leader and now you should have enough votes.
*Vote all on yourself and win!

I'm sorry if I used any wrong words but I hope you all can understand. Please let me and everyone else know if this worked for you as it did for me.