Disclaimer: To help me unlock as many achievements as possible, I used the in game editor which is a additional purchase from the in game store. Therefore this solution is only applicable if you have the editor. The editor does not invalidate your achievements as shown in the steam version.
In order to get this achievement, I went to each of my players, and clicked the pencil icon on the top right corner of my screen. I then selected "Edit Player Attribute details" and edited my players current ability to 200 and their potential ability to 200. To make it even easier I chose a team in a league with lower quality opposition, specifically the Bluefin Sports Championship which is Northern Ireland's second division.
After the end of the season, I was able to unlock this achievement, and I also stacked these other two: