Have you removed the dead body yet?
You need to scrub the floor, walls, and ceiling with some bleach water and then with some overpowering fruity smelling ****.
I would then recommend smoking copious amounts of marijuana until the old stank smell no longer bothers you. When you get tired of that, find a new living situation.
Some smells you can't get rid of. I am a cable guy, I've been in some homes and even though 2 or 3 renters have moved in and moved out over the years, and the house smells the same. I was in some dorms I used to live in 10 years ago recently. They smell exactly the same.