The Curtain Falls

The Curtain Falls is an Achievement/Trophy in Batman: Arkham Knight, as part of the Community Challenge Pack DLC.

Obtaining
Achieve Flawless FreeFlow in every round of the Monarch Theatre, as Batman, Nightwing, Robin, and Catwoman.

Basically, get through all three rounds of the Monarch Theatre AR Challenge without breaking your FreeFlow combo, with every non-DLC character except Azrael. The main thing that'll interrupt your combo is the enemies with shields, and taking damage tends to stop your FreeFlow as well. Luckily, the game will tell you if you successfully pulled off Flawless FreeFlow at the end of the round, meaning you'll get a heads-up if you have to restart.