Mission 15 - Kill Merle Jackson
A handy tactical note- any doors you opened in Perla's last time are still open, but all non-cash assets have respawned- the tac vest, health kit, and upper floor shotgun.
Ignore the front door and sneak round through the parking lot. Peek in and use Intel View + whistle to take out the relatively few patrollers here, ducking back and forth between the parking lot and dressing rooms for cover. Grab the respawned tac vest (can't be too careful), and head upstairs again. Many of the balcony guards can be evaded or ignored, but if you plan to cause a ruckus later, take them down now, to avoid them rushing your back. Besides, a few carry cash.
Retrace your steps to Merle's office- regrabbing the medkit from the bathroom should you need it. The corridor is so narrow you can just walk up to most guards and take them out before they draw. Watch out for the machine gun patroller in the large room outside Merle's office. If you can't outflank him, a quick fusillade of bullets and a sprint to the office will keep any remaining guards off your back.
Merle's holed up behind the desk, but easily visible in Intel View. Later you'll be able to spare higher-ups to run your rackets, but the only way this mission ends is with Merle dead, so take him out. [Q] won't be an instakill in this case- hold down the button to finish him and the mission.