Books that build character tension before you even know who the villain is / hidden villain

Hi, I’m looking for fiction book recs where you as a reader can just tell something is up with a character but you aren’t 100% sure what or why, only to find out they are the villain/they’re evil/they have some big bad secret. ideally fantasy or dystopia but as I’m trying to learn how to write characters like that I’m open to all genres!! Please hit me with your best ideas (though please don’t spoil the person who was just off somehow, I wouldn’t mind but I don’t want it spoiled for others if it can be helped!!)

Thank you ☺️

(For context, I’m a writer – nothing is linked to this account in any way so no self-promo, don’t worry! – and all the ways I have of making a ‘villain’ seem bad before they really influence the plot seem cheesy and lazy, so I’m looking to learn from authors that did it better! Can’t be a writer without being a reader, right?)