My boss at my first job, food service, was Satan. Never came in and when he did he was probably drunk and yelling at the employees, trained me by sitting in the back and yelling insults at me in front of the customers, and yelled in my face and threatened to fire me. A lot of our customers are elderly Japanese and don't speak English well, and my boss thought that if he just said it louder and slower they'd get it. meanwhile me, the employee who speaks conversationally fluent Japanese, is sent off to do menial tasks while he talks to the customers like they're children. The one time I did take over and do a transaction in Japanese my boss got mad at me for making him look bad. I lost so much weight from the sheer stress and misery at that job. They thankfully fired me. There's a reason that place is always hiring and their Yelp reviews are hit or miss.
My current job, handler at a dog daycare, I haven't had that many rude people. We have "escorts" that bring their dogs in for grooming and they're super nice. However there's one woman with two horribly trained dogs (beagle and bulldog) and she's just rude. She hates my boss because he tells her that her beagle is badly behaved and won't let her bring in the bulldog at the same time because they have a bad codependant relationship. She now brings both dogs on the weekends when my boss isn't there so she doesn't have to hear bad things about her dog. That lady's poor wife is so sweet and puts up with such rude behavior. I feel bad for her.