For months i have searched for the many issues about getting the Insanity achievement and the various method to fix it and most of them DO NOT WORK ( Like 60% of the work). I am here to ACTUALLY tell you how to get the insanity achievement for Mass Effect 2. Be warned this is a long one.

You have to play the game 3 times and here is why. The description for the achievement reads "Complete the game on the highest difficulty without changing the Difficulty". the issue with that is changing the difficulty from anything to insanity DOES count as changing the difficulty so it disqualifies you getting the achievement.

pretty much the steps you need to do is beat the game with the First playthrough, then create a NG from the previous PT but change the difficulty to insanity, and then finally create a 2nd NG from the previous Insanity NG and finish the 2nd NG to finally get the insanity Achievement, and now allow me to explain why.

the reason why is because the ME2 difficulty can only be changed during actual gameplay and not the main menu. so during the first NG PT the difficulty is set to what the 1st PT was set at and you need to change it to insanity. once you finish the insanity NG PT, you start the 2nd NG PT and it uses the insanity difficulty from the previous PT. So officially the 2nd NG PT set on insanity with changing the Difficulty is the true PT that that will get you the Achievement.

It took me a total of 4 months to do this research in the hopes it can finally end the the issues people are STILL having to this day. and as of now i am doing the same research for ME3 for the difficulty change issues are the same as ME2, where as in ME1 the difficulty change can be set during the Career Profile menu before the game actually start. I will make a post on whether ME3 has either the same Issue as ME2.