Solasta: Crown of the Magister

This achievement occurs in the Dark Castle when you're first sent to look for gems. After dealing with Lizzaria or whatever it's spelled, you'll enter a blue square to go up a floor. At the next blue square save and enter it, the door by it will open and you can proceed inside to find Aksha. Choose the conversation option to kill her (don't try any dialog checks) and then kill her for this achievement. It'll pop the moment she dies, even if the battle continues.


AntiFederal1 commented that not fighting her during the conversation, and then killing her afterward, does not unlock this achievement, so make sure you fight her through the conversation.

When you meet Aksha you must choose to fight and kill her to get this one.