I scored 4515 points on Civ 6, at Deity level, the highest. For comparison, Hammurabi checks in at half that, and even Julius Caesar only gets 2500! This was playing as Germany, on a large world with a mid-world large lake.
There was a difficult time when the USA made a surprise helicopter attack on me, but I had lots of field guns (they're good for defence, which is necessary when playing at Deity level because the other civs are quite aggressive unless you outgun them), and was able to fend it off long enough for me to put together a bomber fleet. My bombers then broke up the attack, and went on to pulverise America's cities. It was touch and go for a while, but Germany prevailed and I was able to force Roosevelt to a humiliating surrender. After that, it was a matter of conquering the other eight civilisations one by one.
I found a few more bugs in Civ 6; the worst of these is (I think) a memory leak. This causes the game to slow down more and more, and eventually the program crashes. The workaround is, when you feel the system slowing, to exit Civ 6 and restart it.
More minor bugs - when you've achieved all of the civics, it keeps offering you the last two and you get those again and again. When you move an airplane from airfield to airfield, there's no distance limit on the transfer.