Story related. You cannot miss this achievement.
Bear in mind that there are spoilers ahead.
Beat Leia and the achievement is yours.
Just complete the DLC. If you're struggling, try casual. But it is pretty doable in unleashed difficult.
In this DLC, you have two main bosses:
- The first one is Han and Chewie, with them, you simply use Light Saber Throw. Whenever there are grenades and explosives on screen, use force grip into them. This way, you will finish the battle faster.
- The second and last, is Leia, which is a four-stage battle:
- 1st stage: Abuse of your saber, use attacks and Light Saber Throw, this will be down in a minute.
- 2nd stage: You will have to destroy the machine Leia is controlling. Use Force Lightning and Light Saber Throw, while avoiding getting damage by jumping.
- 3rd stage: Use Light Saber Throw when she is high up, then when she comes to the ground, use Force Lightning and attack her, keep with this pattern.
- 4th stage: After the chase sequence where you Force Push her, it comes to the same pattern as 3rd state, just keep with the same technique and you should win the fight.
You shouldn't have problems with enemies in this level. If you're struggling, take cover and abuse of mind trick, so they keep fighting for you.
Also, it is worth notice that you can do this on unleashed difficulty and also win the achievement