This actually is a hard question. I assume it needs to be an industry that is small, doesn't have huge margins and probably is primarily manual labour.
Hmm... Wouldn't be so sure. Some librarians have the power to selectively forgive late fees. They can give preferential treatment depending on their mood or the politeness of the person. You might also bribe a librarian to let you take out books from the special collection.
Public school teachers. Not willing to extend this to admin, though.
Everything single teacher ive even heard of is doing the job because either
They love children unconditionally
They want to raise the next generation to become productive adults who are prepared for the real world
They believe that everyone deserves enlightenment
They agree with Thomas Jefferson that school is preparation for participation in democratic society
Teachers that value money over one of these things typically do not last long.
Just to be clear, most teachers are just doing a 9-5 job they are good at. But if you ask them why they are teaching instead of making actual money in some other field, you eventually drill down to one or more of these beliefs.
I don't think the "natural properties" of a career or industry will be enough to be lowest. I think an industry or career with high oversight from many individuals and regulators. Likely something that has fucked up before, and massively.
Slot machine programmer.
regulated industry
work can be checked many times
customers (casinos) don't want to be fucked
gamblers don't want to be fucked
loads of money to be made doing things well
lots of scary people willing to drop you in a hole
Definitely not that new Jewelry store I saw at the mall the other day, Shauron's gift emporium or something like that. That place look corrupting as can be, they have nine employees working there and they all look wraithlike. Do the employees ever leave the store? There is this one creepy fellow always hanging around in the corners of the store, whispering about some birthday gift he lost or something.