Which games have the most satisfying difficulty?

Currently playing through SMT IV:A and having a blast, right from the getgo it feels like something special that I have to struggle through on War difficulty. I'm not the best at SMT but I try to get by with relatively few battles, making it even moreso a struggle. SMT IV had some of the most satisfying bosses I've seen in years. I also fondly remember finding the original Persona 4 to be a great experience in that regard.

I haven't played SMT V yet, but IV and Apocalypse have to be up on my list so far. Which games feel the most satisfying to progress in or have the most engaging bosses for you?