This trophy is slightly glitched in a good way.
So, if you're not fussed about the benefits you get from completing this and you're playing on insanity.
The trophy now pops just before you reach the DLCs boss rather than after you talk to Liara for the final time in the DLC script.
For those that are, I found you need to use distraction tactics to get it to work. Thabkfully I had my drone as an Engineer which helped alot. Liara's Singularity also stuns him temporarily. You need to get to the Melee cutscene three times in order to complete the boss.
If they correct when the trophy pops in future updates please comment so I can update it.