First, you need to make sure Egor shows up at the party. Travel to The Complex at Noon and disable his device. Then, head to Updaam in the Evening with Shift (Airborne and Reach) and Nexus (Influence). Keep to the left side of the map and clear a path for your return. You will most likely need to avoid Julianna after the party.
Next, enter the party via the side entrance and take out Aleksis by dropping him in the meat grinder for the Alpha Burger trophy. Aleksis will be the one doing most of the talking on the floor of the party with an auto-pistol icon and an uncommon/cool gun. After the woman tells a story about her mother, he will take the stage, and you can press the button on the left balcony to drop him.
Quickly exit the room the way you came in and head to the roof. There you will find Egor and Wenjie. Use Nexus on Egor and wait a few seconds for it to spread. Then, shoot Egor and leave the way you came in.
On the way out, you will need to stick to the rooftops to unlock the tunnels and then work your way around Julianna. She will usually hang out on a small ledge on the right side overlooking the doorway leading to the turrets. If you go around the building, you can sneak up behind her or cause her to move around the area looking for you.
In the video, I messed up and accidently fell of the edge. If I had used Shift to get to the small ledge above, I should have gotten around. Having died, I respawned on one of the rooftops, and managed to leave the area without Julianna finding me.
Once you're out of Julianna's area, hug the right wall to avoid the next crowd and make your way to the exit. The trophy will unlock after you exit the level.
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