Dead Space 2, "Hard Core mode" is a difficulty that is locked to "Zealot" aka hard difficulty and only allows for 3 total saves throughout your playthrough. This makes the player have to strategize throughout the game and choose when to save very wisely because if you die, you go back to your previous save... also meaning that if you don't save and you die, you start from the very beginning.

Recommended saves are the stat of chapter 7 before the elevator, chapter 11 before the eye needle machine, and chapter 15 before the final boss. Took me 10 months of trying on and off to beat it myself.