I've had a lot of shitty jobs but the worst by far was working for a cleaning service called 'Clean Bee.' My first task was cleaning the condo of an 80 year old chain smoking shut-in who died in the tub. The entire floor was soggy. The place was filled with mold and everything was covered in 20 years of tar. After that the cleaning service put in a childhood live in rehab center. I was the janitor and the main goal of this place was to infuriate the inhabitants and then use their outburst against them as proof they were fucked up. I spilled a mop bucket the first day in front of all the kids gaining the nickname Clean Bee. My third day a kid got really upset, the staff yelled out "PUT HIM IN A TACO!" then some giant guys tackled the kid rolled him up in a mattress and threw him in a rubber room. THat was my last day as Clean Bee.
I also worked at a video store where the owner's method of training was giving you absolutely no instruction, then standing over you and yelling 'WRONG' whenever you did something incorrectly. This was mainly done while checking out customers. I no called my second week and he refused to give me my check. I ended up going there at night, pouring a bag of concrete in front of the door then dousing it in water.
Lets hear your work nightmares