Um, professor umbridge from Harry Potter. She’s basically an asshole just to be one.
The other ones all have some sort of justification to their shittyness. Jenny was abused, Vader was a literal slave that was taken advantage of by both the Jedi and palpatine. The joker has literal mental issues.
Umbridge was straight up a child abuser with no remorse or tragic back story. She harmed kids while enjoying it and drinking tea.
I think the original quote was something along the lines of, “the customer is always right, in mattera of taste”. Meaning to accommodate the customers wishes, even if it’s ugly or a bad idea or whatever. Like if they want to paint their house pink with green trim, let them