If you've tried improving on your combat and predator skills in the Riddler's Revenge challenges but you still can't unlock all the medals then this guide is for you.

1. Cheat Engine

You will need to download a program called Cheat Engine[www.cheatengine.org].

2. Arkham City Modication File

Once you've opened up Cheat Engine, download this .ct file[www.dropbox.com] for Arkham City.

3. Loading up Arkham City

Once everything is downloaded, start playing Arkham City and select it as the process to run on Cheat Engine.



4. Load in the Mod File

Now you need to load in the script modification file that you downloaded before.


5. Activating Scripts

Mark these 3 scripts with an X inside the box to active Infinite Health and Infinite Combo points.


If anyone's curious, I did use this method for the last couple of medals that I couldn't unlock.
It is best to play the challenges and enjoy the campaign as normal, only then should you use this method to get the last few medals that you can't unlock yourself.
I don't recommend using Cheat Engine for every challenge as it does take away the enjoyment of playing and your game will probably crash a lot.