The Dark Tower (the last book of the Dark Tower). Did nothing to resolve any of the plot points, literally tells us King is about to do some hacky writing, and then still disappoints when the ending not only has no in universe basis but basically contradicts everything we’ve learned up to that point about it.
Terrible end to an otherwise good series.
Read the whole Dark Tower series. It’s still stuck in my end for how angry I am about the terrible ending.
The Seven Deaths of Evelyn Hardcastle was pretty good up until the end. It wasn’t a bad ending, but wasn’t terribly inventive either and a little underwhelming.
I also finished the Enderlings trilogy. That was an intense ride.