Darkest Of Days

Or you can play the entire game on easy, then once you finish the last battle and are climbing up the stairs to talk to the doctor, simply pause the game and switch the difficulty. Just talk to the doctor and achievement unlocked!

From the games main menu go to Settings. Once your in the settings menu you will see Game difficulty on the top left hand side. Its right under game settings. Highlight it and press A . Press Down on the d-pad to choose With Chest Hair. Once highlighted press A to confirm your choice. Go all the way down and highlight Accept and once again press A to confirm. This will bring you back to the main menu. Highlight New Game and press A . All you have to do from here in complete the game on this difficulty. Good luck!


Alternitive method
Play through the game game on easy and get the majority of the achievements in the game, minus the complete the game on xxx difficulty achievements. You should have 3 achievements left by the time you come to the last level "The Vesuvian Man". Progress through this level like you normally would. After speaking to Dr. Koell he will step into a blue orb and transport to the arena. On your way to the arena you'll have to disable more enemy telesyncs. After killing a shit load of enemies you'll be given an objective "Secure Dr. Koell". Follow the marker. Once your about 30 or so meters from him press start and go to settings. Highlight game difficulty and set it to "with chest hair". Next, highlight accept and press A to confirm. Once at the loading screen you get this achievement along with "Complete Darkest of Days". Congrats!

Play through the game on easy. When you are at the last part of the last level (the Pompeii level), before you walk towards Dr. Koell in the arena (work your way up to the platform on which he is standing, though), switch to "With Chest Hair." You'll get credit for finishing on the highest difficulty. This way you also don't have to actually play any level on the higher difficulty. This is how I did it; works like a charm.

I found a glitch that works very easy. Play the game on normal or easy and once you finish and get the achievement for beating the game just load your last save(Should be the last level).

Go to the settings and switch the difficulty to With Chest Hair.
Just beat that last level on that setting and the achievement will pop.
No need to play the entire game on the highest difficulty.