THIS GUIDE WILL CONTAIN SPOILERS.
-Estimated achievement difficulty: 6/10
-Offline: 60 
-Online: 0 
-Approximate amount of time to 1000: 25-30 hours, +15 for all DLC
-Minimum number of playthroughs needed: 2 (New Game+)
-Missable achievements: Yes, Catch
-Do cheat codes disable achievements?: None
-Does difficulty affect achievements?: Yes (Normal or Hard unlock New Game+)
-Glitchy/ed achievements: None
-Unobtainable achievements: None
-Extra equipment needed? : None
The sequel to the 2009 GoTY, Batman Arkham Asylum. Unlike its predecessor, Arkham City allows Batman to roam free in his environment. The open world experience compliments the gameplay by giving one the freedom necessary to reign terror on the villains and thugs that are encountered throughout the game. There are many villains taking up the star roles however there are even more in the side quests which will take up most of your time, especially the Riddler Trophies/Riddles.
The PC version of the game has the Catwoman DLC as part of the original 1000G (no online pass function), and six achievements have been removed with some of the achievement values changed to make everything fit. The achievements missing from the PC version are:
Step 1, Story:
- Forensics Expert
- Distress Flare
- Ring Ring
- Gotham Base Jumper
- 50x Combo
Play through the story and experience everything that the game has to offer. Play on Normal or Hard in order to unlock New Game+. You can work on grabbing some of the easier Riddler things while you play, but you will need all your gadgets to get the final ones and it is easier to do post-game, so you may as well wait. Same goes for side-quests. See Step 2.
Step 2, Side-Quests/Collectibles:
After beating the game you are allowed to free roam the city. Use this time to do all the side missions, collect all the trophies/riddles and do all the physical challenges.
Step 3, New Game+:
Play through the game one more time but this time the difficulty is basically Very Hard Mode. Enemies are smarter, they have better weapons and equipment, much more difficult encounters, challenging boss fights and to top it all off no counter attack indicator. However, you do start with all your gadgets and power ups so no need to fret.
Step 4, Challenges:
Complete all of the Riddler's Revenge challenges to gain 100% completion in the game, and this should also round out your 1000 Gamerscore.