This is awarded for completing the
Most Wanted mission.
As with the previous two bank robberies, you can make as much noise as you want without any thug noticing, unless they see you. This time, you need to take out 15 armed thugs, before the cash is all gone.
If you have trouble with predator rooms, I would suggest saving a few upgrade points. If you upgrade one of your armor while you don't have full health, it will return all your health as well as armor.
Once you defeat the 15 thugs,
will arrive and you won't be able to do loud takedowns without them noticing. For me, there were two jammer thugs, so I couldn't use detective vision. However, this room is very open and is pretty easy to see what thugs are around you, especially if you use Inverted Takedowns a bunch.
This is exactly like any other predator room, and the "boss" behaves like any normal thug. You only have to take him down once, unlike in Arkham City, where you had to do multiple takedowns.
Once you return this villain to GCPD, the achievement is yours.
If there's any way I can improve this, let me know. Thanks and good luck!