I have a couple fandom friends whose tastes align almost perfectly with my own. If I watch/read/play something where I go "Oh wow, that's really fucked up," I can basically guarantee that they'll be into it too lol. We're all into moral ambiguity, bittersweet or downright unhappy endings, and other grimdark foolery :p

On the flipside, I have other fandom friends whose tastes are polar opposite to mine to the point where I can easily predict if they will like something just based on how much I hate it lmao. For example, when one of them started reading "The Long Way to a Small, Angry Planet" by Becky Chambers, I knew with complete certainty that she was going to love it, only because of how much of an anti-rec it is for me XD