Conarium

Aim for the 5 deaths achievement first and finish the game normally, but make sure you save the game manually in the last level, standing over Dr. Faust and the bowl of stuff you're supposed to drink. Once Glutton for Punishment pops during the end credits/stat screen, return to main menu and start a brand new game, I made sure to go far enough so that it autosaved (exit outdoors), hit the menu button and load the manual save I mentioned above. Drink from the bowl for the short ending and boom, Death-defying should pop during the credits.

I tried numerous workarounds but only this one worked for me, the way this game tracks your deaths across playthroughs is really bizarre.

this is one of those cheevos that go back to the master system way! you absolutely CANNOT die! if you die you have to start the game again from scratch as reloading a save from before you die still counts as a death!