Apocalypse for me
The Last Stand is
Sansa shoulda never signed on for that one
I thought the Last Stand was BY FAR the most disappointing movie in the franchise, especially coming off the highs of the first two. If they would have stuck the landing with X-men 3 then there would have been no need to go back in time to retcon everything and all the rest of those films never would have happened.
X3 butchered the Dark Phoenix Saga (arguably the GOAT X-men story) because it tried to do too much and did so many characters dirty in the process.
They shoehorned the cure storyline in, which should have been saved for another movie.
The Last Stand fundamentally mishandled Jean Grey and Scott Summers, who are the two most important central characters that made that story work. Jean herself got zero character development and was just a plot device. They killed Scott in the first 20 minutes.
On top of that almost everyone not named Logan was either depowered (Rogue), an afterthought (Colossus, Storm, Kitty, Angel, Psylocke), or just not in the movie at all. (Nightcrawler and Gambit)
Not saying that makes Apocalypse any better though. They really should have planned the franchise better because Apocalypse and Dark Phoenix are both stories/events that are too big to pull off with one movie. If they would have planned the movies better out and saved either AoA or the Dark Phoenix Saga for the grand finale as a two part event, then maybe things could have worked.
But instead of doing their homework on the source material, Fox poured all of their energy into trying to make Mystique happen just because she was played by somebody.