TLJ. It could’ve been good, but making Hux into a bumbling idiot, Kylo’s extremely inconsistent character, poor justification of the destruction of Luke’s character, Poe’s degradation despite being the only one who made correct decisions, extremely poor world-building, everything to do about Rose, the incompetent bombers that have no real reason to exist, and everything about Canto Bite just made the movie nigh unwatchable for me. Also, the movie depends on the villains to be complete idiots in order for the plot to even happen. I mean, there’s literally no (comprehensible—the reason the story gives is just unbelievable) reason the first order doesn’t just destroy the fleet with thousands of TIE fighters.
(Not to mention everything about Rey, but TFA shoulders a lot of the blame for that)
However, the biggest issue about this movie is that it was not designed to be incorporated into an over-arching story. The end handicapped the next movie so much that it was required for some major retconning in order to make a movie with stakes work.