I was playing along on v0.952 and winning a war when the enemy contacted me to tell me I am winning... and no he isn't surrendering. Instread he will destroy everything to deny me it. And by everything I mean everything.

Instnatly every single city disappeared, millions of citizens burned down their homes and then commited suicide, every mine, every farm, every remote outpost...

You would think it would take some time or at least someone would say "hey, how about welcoming the conquerors rather then pissing them off by burning everything down"... you would think they would have bulked at the commit suicide part too, down to the last woman and child

A more plausible scenario would have been where such an order resulted in:

Armies: Roll a random number, chance of defecting, chance of disbanding, chance of becoming bandits.

Cities: Every turn make a roll with chance of the city defecting, chance of destroying some improvements (and maybe losing some pop).

outlying improvements (farms, mines, etc) count as city improvement for this purpose.

outposts: Chance of being razed, chance of defecting, chance of being simply abandoned (left empty to be claimed by the first player to step on it).

Also, I don't know if this game has a "surrender to ally" trick that AI pulls but that is total BS and should carry repercussions. Specifically, the side being surrendering too should automatically become at war with you, and they refuse to accept the surrender if they don't want to go to war with you for some reason (eg: they are your allies)