The deeper I get into W40k the more I realize that this isn't a " god has abandoned us" universe and the god is the one with the magnifying glass burning you.
Another nightmarish job in WH40K are the ship refuelers, the guys responsible for replacing the nuclear cells on human ships. The fuel pools are so incredibly radioactive nothing survives, even Ork spores, and because of it, no machine nor servitors can do the job, the radiation fries the circuits. It need to be done by a 100% meat refueler. Every time a warp engine needs refueling, an literal funeral procession walks into the fuel compartment, with the refuelers wearing ritualistic funeral robes. While refueling their hands start emitting black smoke, their faces melt and their body burns like a 3D very bad sunburn to literal ashes. The refuelers know they're dying for sure. The lucky ones. Sometimes the refuelers mutates while melting into a disform living mass, crawling on nuclear pools, too radioactive to be decomposed by bacteria or fungus.
Sentient Servitor: Whether done intentionally as punishment, or the Mechanicus didn't lobotomize you properly, you are fully aware and conscious of your fate as a servitor, but unable to control your body. You are permanently locked in your own mind, until your cybernetics eventually give out, or you're destroyed for whatever reason.
Note that, flesh whithers but iron stays eternal, so that natural death you're looking for can be an upwards of 100 years, if the tech priests bother to give you regular maintenance.
The first one is literally the plot of Warhammer Darktide, only that because you and your party are the main protagonists, you survive mission after mission until you're incredible and well respected soldiers of the imperium 🥴
Fun fact: arcoflagellants greatly vary in destructive quality, depending on the severity of the wrongdoers crimes. Some have automatic systems that do their handling, making them valuable expensive bodyguards for important people. Some are dangerous enough to take down space marines.