Age of Mythology: Retold

This actually unlocked for me after the third mission, not the first. This bug also happened for the Trident campaign for me. Might not be applicable for everyone, but in case you need to rush this specific achievement for a challenge or something, just wanted to let you know.

Edit: Thanks to oONeonDemonOo's comment, it appears you have to quit to the main menu for it to unlock.

For the scenario itself: Up to the north is a small encampment. There is someone who wants six cows. Bring them to him, for that he opens a magic pathway almost right next to your goal. There are two walls and a towncenter in the way between you and the goal.
What I did was built up a small force, mostly melee units (around 20), your hero and a couple of dwarves. Then we went through the gate, punched through the first wall. Then I was attacked by units, so I used Frost, freezing them in place. While they were frozen, I punched through the second gate. The Dwarves built some oxcarts in the goal area and I was done.