Here's yet another one of those pesky multi-step time sink achievements, but the reward is great. To get the 'Genius' achievement in Batman: Arkham City, you have to rescue all five hostages The Riddler has taken. It should be noted though that you'll need a certain amount of Riddler...
It’s worth noting that you can lock achievements again and again using the same method. Simply deselect the achievements. There are few reasons why you would want to do this, but it is still useful to know that you can. Get All the Steam Achievements With None of the Work With SAM, ...