the thing that makes it smell the worst is the release of ammonia and ammoniac compounds, second worst factor is the decay of the fatty acids, which get that acrid, rancid smell, the two things together, ammonia and rancid fats, is more or less the signature of "rotting dead bodies" you can't really make it go away entirely. it's always been a thing i've noticed in some houses and some kitchens and not others, if they have bad ventilation and fry a lot of meat the walls get coated in condensed grease that oxidises rapidly.