This achievement is glitchy, and might not unlock for you after unlocking all the other achievements. My last achievement had been Resistance Hero, and I sat there waiting for this to unlock as well, which it did not. I then went and cleared my cache, turned off my Xbox, and loaded up the game and it still didn't unlock. So what I did next was load up the last part of the game on the highest difficulty, defeat the boss, skip all the cutscenes, and wait until the end credits finished, and when the after credits cutscene played that was when it finally unlocked for me. So if anyone has a problem getting this to unlock after you unlocked everything else in the game, try this method.