After beating the game on Realistic difficulty, I did not get the achievement for doing so. I looked around and found that I was not the only one with this problem. It seems that the first patch for the game is causing the achievement to not unlock, even when the entire game has been played on Realistic. For those that are having the same problem, here is the solution that worked for me: 1) Go to the Memory section on the Xbox 360 Dashboard. 2) Click on the hard drive and press Y to bring up the device settings. 3) Clear the hard drive's cache (this will clear the update for Conviction). 4) Start up the game, but DO NOT install the update when prompted. 5) Play the last two scenes of the game on Realistic (without installing the update, you will be forced to play offline). 6) The achievement should unlock right before the credits roll once you beat the game! I did this earlier and was able to get the achievement so I can confirm that it works. Once the achievement is unlocked, you can then install the update the next time you load up the game.