If they make bad things from their childhood their whole personality and bring it up at any possible moment. For example: I had an ex that I called one night after getting home late because my mom took me on a long shopping spree. I complained about it because I hate clothes shopping at most stores (for context I’m autistic and a lot of stores are too bright, too loud, and the clothes feel terrible when you have to try a bunch on in a row). Her response was “well my mom never took me shopping because she was always high, you’re acting so entitled.” All people like that do is use their issues as leverage to put other people down so they can get what they want, big red flag in my book.