found some save here with Impossible/ironman ending already, but you need to own the DLC, which I don't. I've downloaded a modified starter save from this site ( credits go to ZaqXavier for creating it), played the game to the end.
Here I offer you the ending on Impossible/Ironman playthrough! Just move the soldiers to the final location and kill the final boss (should take about 2 turns, as I said, the soldiers are quite amped up).
What achievements will this unlock for sure?
- Ain't no cavalry comin' - have a soldier survive every mission
- No looking back - beat the game in ironman mode on Classic or Impossible
(these I certainly got from this save, I have completed the game already in a different playthrough)
That said, it should unlock these achievements too (not guaranteed, not tested, already had these before):
* Our Finest Hour - beat the game on impossible
* Earth first - beat the game on classic
* Humanity's savior - Beat the game on any difficulty
As usual, rehash & resign.