In the Union Strikes Back gig, Rogue will ask you to take out a character called Vic Vega. He is running some shady security company that is really just a bunch of hired thugs.
They are trying to strong-arm a worker’s union into backing down from a strike, and Rogue wants you to cut the head off the snake. The first thing to know about this mission is that it is buggy, so make sure you keep a save point at the start of the mission in case something goes wrong.
The first thing you need to do is get a keycard that will allow you easy access to the building. This is a simple task. Walk in the front door and use a Distract Enemies quickhack on one of the screens behind the receptionist. You will be able to see a keycard on the desk in front of her, so grab it when she is not looking.
From, go back out the main entrance and head right, to a side door near the street at the back of the building. Use the card to open this door and step inside. You will be in a small garage, with another door at the back of it. Just inside that door, you will find a security guard. There is a wall between you, but it is mostly glass, so duck low so you are not seen. Now, how you approach this is up to you. If you have the System Reset quickhack, you just use that to shut her down.
If not, you will need to go for a Distract Enemy hack, then sneak into the room and snap her neck. When she has been dealt with, interact with the computer console to lock down Vic Vega’s location, and get a new map marker.
You will need to go upstairs to take the door at the end of the hall, on the left when you leave the smaller security office. Go upstairs, but stop at the top and wait for two people to finish talking, then return to their desks. Now, sneak down the right side of the room, being careful of one enemy walking around in an office there.
Vic Vega’s office is at the very end on the right side, and if you time it all perfectly, you can sneak in, snap his neck, steal his stuff and then jump out the window without anyone knowing you are there.