Make sure to have at least one steak in your inventory towards the end-game
The first time you meet the strange creature is towards the end-game. There will be a few cut-scenes with major spoilers, and you'll be face-to-face with the creature afterwards. You'll see your character crawling away from said creature who will be slowly getting up. Once you can control your character, access your inventory (
), select Equipment and select the steak and throw it in the creature's general direction. The achievement will pop up shortly after.
Additionally, if you have the rifle as well, you'll have enough time to score a hit after throwing the steak, which will net you the "Bulletproof" achievement.