This achievement can be obtained as early as Mission 2.
Once you have been introduced to your three main powers - Displace, Semblance, and Foresight - during this mission, you will ideally want to find an idle guard. Once you have a target in sight, activate Foresight and deploy a Displace marker behind the target using . Now exit Foresight, use to swap positions with the Displace marker, and be ready to kill the target with your sword.
If done correctly, the achievement will unlock after the target has been killed.