Requiem for a Killer

Requiem for a Killer is a Trophy/Achievement in Batman: Arkham Knight, as part of the Community Challenge Pack DLC.

Obtaining
When playing as Batman in the Iceberg Lounge AR Challenge, defeat "an old adversary."

Sometime after the player reaches 1,000,000 points, Killer Croc will jump in from the sidelines and join the fight. He acts similarly to the way he does in Beneath the Surface, and the player can't damage him right away. After defeating a few more enemies, Nightwing will appear and join the fight. Once he joins, the player can defeat Croc the same way they did in Beneath the Surface. Croc is only fightable when playing as Batman, and won't jump in if the player reaches >1,000,000 points as anyone else. Even if other characters could fight Croc, the achievement specifies that you must play as Batman to get it.