I played Mass Effect until my soul bled. It's probably my most played game of all time. I played it through when I first got it on my old Gamertag til I had all the achievements except a couple of ally achievements, some of the engineer achievements, and the Hardcore and Insanity difficulty setting achievements... I played it about 3 or 4 times through to get that.
Fast Forward a couple years, I hadn't played it for a while, I had a new gamertag with NO Mass Effect achievements on it, so I sit down to try and get them ALL.
I play it through once on Hard, unlock Hardcore mode, getting 100% completion for the first 2 ally achievements. Play through it on Hardcore, unlock Insanity mode, getting 100% for the second 2 ally achievements. Start to play through it on Insanity mode... realize "fuck getting 100% on Insanity, that's crazy", and just barrel through, beat it on Insanity.
Then I play the game through AGAIN on easy for the last 2 ally achievements. Then I play the game to level 10 as an Adept and get all the Adept achievements, then play to level 10 as an Engineer and get all the Engineer achievements.