In the lobby comboin' your dudes Achievement
In the lobby comboin' your dudes10
Scored a combo higher than 40 before they locked the elevators
This is "Job One" level. Simply get a combo of 40 or higher before they lock down the elevators. This is pretty simple, especially so after you've upgraded your skills some. The Sais are great for combos. You'll get a checkpoint if you kill all the enemies and the elevator locks down, so you'll have to restart the chapter if you progress to far without getting it, but this is near the beginning of the chapter, so it's not too far to trek to get back to it.