I'm not a completionist. I have little interest in getting all the achievements in a game and my interest for a game usually drops after I finish it.
However, there's one game that I have been playing for a long time, and where I only have one missing achievement on Xbox, and that is Rayman Legends. I've finished the game, I've replayed all levels multiple times, and my entire family is still playing it together. If you don't have a soft spot for Rayman, it's probably because you were not 12 and French when it came out. But Rayman Legends is a great platformer, it's still absolutely gorgeous, and it plays great. My last missing achievement is reaching level 11 in Rayman Legends.
To get to level 11 and get 100% achievements in Rayman Legends is a bit of a grind.