GnK? Theorically, i should do this :
-Settle on a mine tile, sell luxury
-Get Honor and the free gg
-Steal a worker from a cs
-Buid 2nd city right close to his capital and buy tiles so that you can put a citadel the closest as possible. You might want to keep the gg if there is almost no units in his cap
- Improve another lux, chop forests, sell and DoW(allowed under HoF rules since you gonna get his capital)
-Build/buy archers and 1 scout
-Put scout close right before you gonna take his capital. He will likely want to kill the weakest unit, the scout, letting other units healthy(and the initial warrior)
-Win
At deity you probably need construction before taking any actions(putting you near the 60 turns mark at standard speed)
Is that strong and fast enough? I'm not sure but it seems good on paper.
Vanilla?
-Settle on a mine tile, sell luxury
-Get Liberty and free settler
-Steal a worker from a cs
-Settle city right close from his capital
-Improve another lux, chop forests, sell and DoW(allowed under HoF rules since you gonna get his capital)
-Build/buy warriors
-Win