For me it'd be The Red Queen by Victoria Aveyard. It really did have an interesting premise, but it just turned out to be another generic YA fantasy. It had the opportunity to bring up some really interesting points about society and the government (I guess), but it ultimately didn't. Worldbuilding isn't good. Mare Barrow, the protagonist, was boring. It has one of those romances that I legitimately did not care about. It's a forbidden romance sorta deal, which is funny because I typically don't mind and sometimes even like forbidden romances.
Oh yea I just remembered - it has one of those shitty plot twists. It's like a modern-Disney, Frozen-level kind of plot twist except it's magnified to a certain degree because it's allowed to show blood and stuff.
I hear the other books are better, but my rule is typically "if the book really didn't catch my attention, either ironically or unironically, then I'm not reading any book after that."
[Edit: I keep editing this bc I keep remembering stuff I don't like about this book, it has a love triangle. A poorly written love triangle, at that. My absolute favorite trope that absolutely does not make me want to roll my eyes into the back of my head so I can see what kind of brainrot has accumulated back there.]