It started strong, then they proceeded to bring in too many characters, not develop them enough, failed to kill silverfox at the appropriate time, and the worst most unforgivable thing they did:
They ruined Deadpool.
UNFORGIVABLE, they completely completely butchered his story and downplayed his personality and style. Screwed, that's how I feel, I had two favorite characters in this movie Gambit and Deadpool, Gambit barely got any screentime and absolutely NO character development and Deadpool end being screwed up so royally it isnt even funny.
Oh, by the way, you know how you always thought characters with regenerative powers could die if shot in the head (in wolverines case in an area without adamantium bone), or with an adamantium bullet, or if they got their head cut off? yeah none of those work. Essentially there was no suspense or consequence of any fight involving: Wolverine, Deadpool or Sabertooth.
How can I care at all when Wolverine and Sabertooth are fighting when they are shown being shot and blown up in major wars for the opening sequence? it is made abundantly clear that close range gunshots to the body and head do nothing, hell it turns out the worst you can get out of gunshot wounds to the head is amnesia. So go see this movie if you like invincible characters causing things to blow up and characters with potential to become dead, do that, go watch it if you want to see the most franchise ruining since XMen3.
If you need one sentence to keep you from watching this movie, its this:
"Deadpool gets an adamantium skelleton with retractable hand Katanas as well as wolverines regenerative healing factor, Cyclops' optical blasts, teleportation and still after getting Decapitated manages to survive in the after credit bonus scene to allude to his anti-climactic return in some other butchered Xmen movie.