One time a woman screamed at me because her kid was tearing open a toy before paying for it and I kindly told him to wait a little bit.
She seemed on the fence on whether she wanted to buy the toy or not for her kid, so you know I wasn't glad that her kid was already ripping it open.
She then proceeded to scream at me for being "really awful with kids", "a horrible person", "bad at my job", etc. Also she wanted to complain to the manager if I ever talked to her kid like that again. She then angrily paid and walked of the store.
Also people tinkering / modding their console and then trying to return it because it doesn't work anymore and angrily insisting on having it bought that way in Gamestop.
Source: https://www.reddit.com/r/AskReddit/comments/bicr5z/gamestop_employees_of_reddit_what_are_some_of/em02p9a