Well, once I played as Greeks on an archipelago with a lot of islands. I was on a large island group all alone, so I grew as quickly as I could to dominate the island group. Well, good. No problem, no one else here. I focused on peaceful growth and trade, trading my ivory and gems for spices and so on. I also found some outposts on several other islands, which quickly become local power points and navy bases. Other countries find their own cities near my territories, which I then assimilate because of my superior culture and democracy.
North of me is an Japan/India combo and English mainland, east of me Iroquis and Germany and west of me my worst rival, America. As soon as I can I build a huge tank army and transports with marines and focus them around tactical points all around the world. So, theoretically, I could quickly ensure my dominance over key points in the case world situation deteriorates.
It does, but because of me. I HAVE NO URANIUM, FFS! Well, USA does have 4 deposits. They cannot trade with me, because they haven't found it. I cry, but it's, after all, best of me to have uranium and let USA have techs for nukes. I have no choice - they are the only uranium deposits IN THE ENTIRE WORLD. So I give them fission and ask for uranium.
Lincoln: "No."
Me: "What?"
Lincoln: "No, no uranium to you, lalalalalalala."
Me: "Prepare for war and genocide!"
So I roll my entire massive army over the USA, razing cities and bombing them as I move. Other civs become enraged to me, but what can they do? I finally force USA to it's knees, he handing over all his colonial states and all but 3 cities. I then hand over gold and techs to them, you know, better to be a good winner. I try to avoid trouble.
Years pass and I build my nuclear deterrent to stage of ~300 ICBMs and several hundred tactical nukes. This brings my economy to it's knees, so off to the communism we go! Other countries become a bit cautious, because huge and apparently aggressive communism state with hell of a lot of nukes and a huge army - and totally dominant culture - is busily securing world dominance near them. I, however, manage to keep them happy and maintain peaceful relationships. World is at peace. Everyone's more or less happy.
Then USA, in their normal arrogant manner

declare war on me. Because, you know, 3 cities with mech infantry are always a challenge for several dozen stealth bombers, modern tanks and radar artillery. Sadly they accept no peace, so I crush them like worms they are. There we go - my technologically worst adversary bites the dust.
Rest of the world flips out, maybe cause I razed America's capital, and declares war on me. I immediately lose several of my farthest outposts because my buildup of nuclear deterrent. I seal off my own colonies and stop every assault they throw on me.
Then, magically, Iroquis manage to infiltrate my outer line of defence and burn New Troy, one of my regional capitals, into the ground. So I ask them to accept peace or be destroyed. Foolishly, they say "no" to my offer.
I nuke them to the ground and launch and all-out assault on them. World pollution reaches critical levels. Everyone declares war on me. One tactical nuke takes out two of my marines in some ****hole on the other side of the world.
The rest is then what is usually referred as to "one-sided nuclear holocaust". My ICBMs and tact nukes demolish all other cultures at once, and then the rest of the war is my army trying to cut through their adamant defences ->gets thrown back -> nuke the defences -> try again -> nuke more.
Finally the world pollution becomes so horrible my coastal cities start to fall. I am forced to end the game, because other countries started to use nukes as well.
GG JANOS, I WILL NOW GIVE YOU THE ULTIMATE POWER OVER THE WORLD'S NUCLEAR FORCES DURR DURR
