Choose Select Level
Press Y to skip the cutscene.
The guy say, "Max, stand still and get crushed." Just follow his advice and stand still and keep getting crushed. Each of these is a death. You will have the achievement super fast, and you do not need to do anything, other than leave your controller on and walk away for a while. Best to attempt after the game is completed and all achievements won, as I only had 33 deaths left when I started this.
Here is a video I made to show you how I did the last 33 of my deaths after I had beaten the entire game and done the other achievements with gamerscore.
You don't have the watch the full video. I just made it long to show you guys that it keeps working, and show me actually unlocking the challenge.