I have heard of a few people having problem with this achievement, with the game force closing at the end of a run and it does not count the death.
turn your internet off when playing.
I play this on my windows 8 laptop. and it did the same thing. I did some research and have discovered that. The game is force closing for some reason when it tries to access the leader boards at the end of a run.
Thus, turning off the internet will stop that from happening.
once the achievement has unlocked. you can turn on your internet again and after about 15 minutes (it took about that for me anyway) your xbox app will synch and update with the new achievement!
If you have any questions, please pm me or comment here :) Happy hunting.