I'm still not sure how to feel about 10 Cloverfield Lane's ending. I haven't decided it's even a bad ending, it's just such a... derailment. I enjoy how the ending actually got alluded to way earlier in the movie and I like that "wait, what!?" feel, but it's just so... completely different from the rest of the movie it sort of makes the movie feel like it goes nowhere.
I really liked where "I Saw the TV Glow" felt like it was going and I was pretty invested, and I absolutely HATE what it ended up being and how it was handled. I felt lied to by the advertising and everyone who had recommended it to me.
If it counts, I really like the opening of The Dark Knight Rises and a fair bit of the first half, but that movie rapidly becomes a bit of a dumpster fire that totally sabotages itself by trying to be unexpected as well as trying way too hard to up the last one. It's just a mess.
One I saw recently that I honestly didn't really care for in general was Pom Poko. The reason I bring it up is the very ending, like the LAST line of the entire film. The whole movie is super heavy handed about a specific message, the entire plot is entirely focused on this ONE ideal... and the final line literally has a character look at the screen, break the fourth wall talking to the audience, and basically say "Yeah, that message doesn't matter." So while it's not a movie I liked that suddenly gets ruined, it's a movie I was pretty "meh" on that made me unexpectedly hate it.