Diplo Victory in 1840AD ~27k points
I left off my spoiler in 500AD with the Incans having just declared war on me.
I destroyed their invasion forces, then sent a couple galleys with cats and Berserkers in them over to his continent, protected by a trireme. I found to my unhappiness that I cannot bombard from a boat

, so I landed my troops, bombarded down the defenses, and took Cori...something in around 1000AD. Since we had very little production, I heavily poprushed my troops as fast as I could. I built 5 galleys and ferried over troops whenever I needed to. Huayna was not a very amphibious war simply because I was unused to both warring and not needing to worry about amphibious assaults.
Vilcas was razed amphibiously, Macchu Picchu was conquered, Huamanga taken and lost again, Ollantaytambo taken, lost, then razed, Tiwanaku taken, and Huayna refused to surrender...so I took Cuzco. It was a risk because I used the last of my troops, and if I lost, or he counter attacked, I would lose effectively my entire army on his continent. Luckily, I won, took Cuzco, and he was immediately willing to Surrender and become my vassal.
Thus, I moved all my transports back home, used the two Great Generals I had produced to build a Military academy and an Instructor in Birka, my horse city.
At this point I was getting greatly outpaced in tech by pretty much everyone, and somehow was pleased or friendly with everyone. Despite being Buddhist with Izzy, religion didn't seem to affect the relations I had with everyone. I decided then to head for a diplo victory, hoping I could get Caesar to be my opponent, since no one liked him except Asoka.
Unfortunately, as happens with plans...they got mucked up by a couple things. First, Caesar began running away with the wonders and tech race. He and Asoka were the first two to Liberalism, and for some reason I began getting the WFYABTA block from everyone...I've never even had that before, yet everyone, even Izzy who was +18 with me, was giving that to me. So...I began scouting out various lands for a good target for my now semi-numerous and very upgraded Berserkers. I had Theocracy, Vassalage, a Barracks, and an Instructor in my main military city, allowing me to produce 9exp Berserkers once every 11 turns, 6 once I built the Heroic Epic there. Caesar's name came up short...he had good production it seemed, since he had built 8 or 9 of the wonders, he was universally disliked, and was close enough for me to conquer him. He also seemed inclined to build Praetorians rather than Maces.
Thus, I sent my galleys through his waters into India, then declared war on him in around 1400AD. On the first turn of war, I conquered Rome, on the second, Arretium was taken. I then moved back toward India and razed his two Eastern cities. Just before that happened though, he discovered chemistry and started building grenadiers...bad news for my Berserkers! I decided to give him no time to build up his gunpowder troops. My trebs and Zerks moved quickly along the coast aboard my ships, landed, bombarded, then conquered city after city. Ravenna was razed, Cumae conquered, Neapolis conquered, then I took an ice city...the Christian Holy City. I took it because without taking it, Rome would never work its entire fat cross...but I really didn't want it. It gave me 9gpt thanks to the shrine, but I planned to gift it to Asoka.
As soon as I took the christian holy city, Rome was willing to surrender. In all, I took 8 wonders from Caesar. It is interesting to note...at this point I still had not gotten a single Great Person...Rome gave me one 5 turns after it came out of revolt. A GE that I used to build Versailles in Macchu Picchu.
At this point I had 2 vassals, Izzy at +17 and Cathy at +10. Roosevelt was my likely opponent and was +7 with me, while Cathy was +8 with him. I decided for some reason I'm not sure of that perhaps I would attempt a conquest win...I only halfheartedly thought this, but while thinking it I realized Asoka had 2 LB and a pike in all 4 of his coastal cities, including Delhi.
Thus, I declared war on him with my highly upgraded Zerks and Trebs(I only had 8 Zerks and 6 Trebs, but nearly every single unit had CR3, and 3 of my Zerks were CR3, Combat2) I therefore, positioned 2 Galleons(I upgraded at some point) outside of Asoka's 3 noncapital coastal cities just before declaring. Upon declaring, I brought in my troops and landed them at 2 of the cities, conquering the other from the sea. India counter attacked, but didn't really do much good. I bombarded the other two cities and conquered them the next turn. Following this, I loaded up my ships and moved over to Delhi, where I bombarded the city...and found something disturbing...There was a Machine Gun sitting in the city.

I worried about it for a moment, and decided to try my Trebs on it...perhaps they would hurt it a little bit. WHOOHOO!! I lose one treb, but my second one somehow WINS! I easily destroy the LBs and conquer Delhi, giving me another 4 Wonders...3 of which are already obsolete lol
However, cultural pressure and the lack of a willingness to surrender by Asoka, meant I had to go inland. I razed the Taoist holy city and just before I razed Lahore, an ice city, Cathy declared war on me!

. Lahore was defended by a Machine Gun, 3 Rifles, and an LB...that caused me to lose 1/3 of my troops, following that, Asoka surrendered and I was able to pack up and send my troops back home.
I got my troops home to find that my easternmos gem city had been overrun by Cossacks, Rifles, and Trebs. I quickly began rushing troops in Birka, Uppsala, and Haithabu while transferring the Lbs defending each of them to my gem city. Unfortunately, it didn't help and Cathy razed it. I was able to rush a few muskets, give them gunpowder promotions, and destroy the remaining Russian troops, but I'd lost a size 14 city

so I retaliated by sending my Indian vets to Russia. I went 0% science, upgraded 5 of my Zerks to Grenadiers, and razed Novgorod, a size 13 city. Cathy was immediately willing to give me 500 gold, 7 gpt, and her WM for peace.
I then found out I can tell my vassals what to research

I had Huayna research Chemistry for me. By this point I had gone from 0 Great People in 1450AD, to gaining a GP for the Jewish Shrine, 2 GS, and 2 GE. I used one GE on Versailles, and was saving the other for the UN. I used 1 GS eventually on Biology and the other eventually on Computers.
From that point on, I teched up to Mass Media, built the UN in 3 turns thanks to a GE and 2k gold from Izzy and Roosevelt, and easily won the SecGen election. I only needed 476 votes to win the diplo victory, so I discovered Bio, gifted it to Izzy, Asoka, Caesar, and Huayna, since I was guaranteed all their votes, and hoped for the best. Unfortunately, I came up at 420 votes...40 short.
There was absolutely nothing else to be done...I had been continuing to build Zerks, promote them twice, and then upgrade them to Grens, so I loaded everything up and declared war on Cathy again, then bribed Roosevelt into warring with his only supporter for Mass Media

Then...bad news. Cathy wasn't using Rifles anymore...she had upgraded to Infantry and I couldn't built them yet. Asoka and Caesar knew how, but refused to share
Thus, my amphibious grens and my trebs started to move toward Rostov...but then I saw the horrible horribleness that was a stack of 6 destroyers and 3 transports in Moscow. Unfortunately, it was defended by 2 Infantry and 5 Rifles as well. I used my frigs and Ironclad to bombard the city, then suicided every single treb I had. It didn't do squat to one of my Infantry, but hurt the rest of the stack. I then suicided half my grens before I had managed to kill off her Infantry. Luckily, Rifles are easy prey for Grens, so I managed to take Moscow. I then had a choice...do I keep it, as such a nice city as it was, or do I raze it? It was really no choice...I had no way of defending it and didn't have anywhere near the technology to conduct a fair land war. I razed Moscow, size 21, and was instantly much closer to a diplo victory. Cathy immediately resettled there, but obviously the damage was done to her. I finally managed to get Infantry from Caesar for Radio and Computers, and was no longer able to build Zerks

Luckily, I had cannons now. To make a long story short...I conquered a size 12 1 tile island city using my amphibious grens, then upgraded them all to Infantry, went 0% science, buying 3 cannons every turn, and then razed Yekaterinburg, size 9, and Rostov, size 8. I originally kept Rostov at size 14, hoping ti would enable me to end the game, but Cathy came up with a tank

and took out my 2 defending Infantry. So I then went back and razed Rostov. This happened the same turn as my last election. I won the game in 1840 with ~450 votes, with 443 needed.

This is my earliest diplo victory in a solo game

It wasn't nearly as fast as it could have been if not for a few mistakes, but overall I am proud of it.
Biggest mistakes: Trading for Chemistry when I did...I had planned on using my 2 GS for Electricity, but lost the ability to when I got Chemistry...it made them prefer Bio. If I'd lightbulbed Electricity, it would have saved me over 25 turns.
Warring Asoka...it wasn't really necessary at the time, and actually led to Cathy attacking me, as he was her friend and I believe he bribed her into it with Rifling. If not for that, I could have had Cathy's support once she switched to Free Religion.
Not building any monasteries the entire game. If I'd built even 1 monastery I could have converted Cathy to Buddhism easily, giving me her votes instantly.
Peacing Cathy when I had a sudden army of 10 Amphibious Grens. I could ahve easily taken/razed at least 3 other cities, reducing the number of votes required enough for me to win on the first election.