Age of Empires II: Definitive Edition

As usual set your difficulty to standard and should be an easy achievement. You have more than enough time to concentrate on your economy first. 60-70 villagers should be enough mostly on food and gold cause we are going to make unique units only. Also a lot of stone around your base to mine, so we can start to mass from more castles.
When you have cavalry fully upgraded, unique units will destroy everything from yellow (found north) even though he's in imperial age. More you have in a group together, more attack it gets (18 attack in castle age). You can add some rams to kill faster but it's not really needed.

Achivement should pop after yellow resigned, the mission is completed same time anyway.