Bugged achievement.
If you still wanna get it, try following the steps below (dunno what are the mandatory ones)
- get the villagers at the engineer village, but dont destroy all the buildings
- set your city at the far east of the map, rush imp and kill yellow before 40 min (mostly skirms and trebs)
- DONT DESTROY THE MARKET AND THE 9X BLACKSMITHS, raze everything else (not the walls)
- destroy a few towers on the china wall
- raze blue city
- kill green, then red, then teal
- don't get the bombards
There seems to be no difference if the ennemy is "defeated" or "resigned"
Hope it helps