Annoyed with people's lack of empathy for their treatment of a complete stranger. (If that's the right word to use, empathy) Being a complete dick to a stranger is bad enough, but what people don't realize is that the stranger may remember what you did to them. I always hear "Ah, don't worry about it, they'll forget it later today or tomorrow." Which can be mostly true, but I have a fear of seeing them again in the near future. I don't act out on a complete stranger that did something that upset me to make myself remembered by them for that reason. No one ever thinks of the consequences of their actions when interacting with a complete stranger, you could see them the next day at the same grocery store or local event.
One example I can think of is going to a gas station that had a few disabled gas pumps. I saw a FedEx truck driver parked at a disabled one, sitting in the driver's seat on his phone and hazards lights on. I pull up to the functioning gas pump in front of him in a vehicle from my dealership I work at, next thing I know he looks up and starts having a complete tantrum over me taking "his pump." I was rather annoyed and confused as to his tantrum at first, but realized he wanted the pump I was at and was waiting for. He was screaming in his truck, flailing his arms around, giving me a death glare, etc. Rather than confront, I drove to a different gas station to avoid his crap. The next day, I saw the exact same FedEx driver delivering car parts to my work's parts department and I almost felt compelled to confront him about his unprofessional behavior at the gas station the previous day or just report him. (Kind of wish I did)
Wish people would think about how they treat others before doing something inconsiderate and stupid. But people seem to think they have no consequences when doing something to upset a stranger that they think they might not see again. I've honked at people for cutting me off and giving me the finger for it, only to find out they pull in the same exact parking lot as me for something like a grocery store. If I was some nutjob, I'd probably do something stupid when confronting them about their action, but they don't seem to consider that. Somedays I wish these types of people face a consequence that will "teach them a lesson," and make them realize there's someone crazier than them.... Not wishing harm, but someone who'd confront them about their inconsiderate actions.