The other achievements in this game are situational (similar to Madden 10) or beating the game at various difficulty modes. Some of these make perfect sense, others are a bit random.
Big Bang – 50 pts
Complete the game on easy – Pretty self-explanatory. Don't do this though, see next achievement.
Bigger Bang - 50 pts
Complete the game on normal - All things considered this game isn't that hard on Normal, either. The nice thing here is if you beat the game on normal, you automatically get credit for beating the campaign on normal mode as well.
Biggest Bang - 50 pts
Complete the game on hard - After this, you'll wish it was worth more than 50 points. If you're crazy enough to do this first, you will get the points for beating it on the lower two difficulties.
Night Glider - 5 pts
Glide continuously for over 100 meters - An outside environment or the larger rooms where you hunt down henchmen are the best locations. Thought its only worth 5 points, its a bit more difficult than it seems.
Party Pooper – 10 pts
When you finally get to the Joker’s party, remain outside the visitor’s center, don’t walk through to the next area until you’ve dispatched the henchmen. This is also a great place to pick up the 20 hit combo if you haven't already.
Rope-A-Dope-A-Dope – 10 pts
String up one henchman and cut him down to scare another – You can only do this once you’ve gotten the inverted takedown upgrade. Wait until you get a guy hanging from a gargoyle, then break the rope via batarang when others are nearby. Besides getting the points, its also incredibly amusing.
Mano-A-Mano – 10 pts
Take on a beast in hand-to-hand combat – Beating a Titan without using a batarang. Yup, this is just as fun as it sounds. Best do this when you have multiple Titans, dodge them and wait until they rush each other, then go in for the kill when they’re stunned. You only need to beat one to get the achievement. I would do this during the first battle with Titans, the second one is far more difficult.
Catch! – 5 pts
Catch a batarang – Once you get the remote batarang update. Throw one in an open area and direct it back to Batman. If you try this in an enclosed area, the batarang will crash into a wall.