For those of you that are stuck at 96% can try what I did when mine was stuck. First make sure every mission is complete 100% and then load up the last mission. Can be played on easy to breeze through. After beating the boss and
, I didn't skip any cutscenes. I even let the credits play through. You may not need to play the credits but I did just in case. After the credits are over, a new cutscene will start.
After this cutscene finishes. The achievement should pop. That's where mine did. Hope this helps those of you that are stuck with 96%. Good luck.