15. Thor: The Dark World
Despite hiring arguably the perfect man for the job after Kenneth Branagh didn't return for the sequel in Game Of Thrones and TV veteran Alan Taylor, Marvel scored their biggest misfire with The Dark World. In hindsight, Terminator fans should probably have taken it as a warning for the God-awful Genisys, but you can't win them all.
The sequel actually has some good ideas, including casting Loki as a Hannibal Lecter captive type, using the death of Frigga as an emotional hand-grenade and the integration of the Aether. And you do have to give some props to the attempt to introduce a race of vengeful alien elves with the power to evolve into berserker monsters (it's not their fault the execution was so iffy)
The script is terrible, Christopher Eccleston is relegated to a Doctor Who monster of the week and Taylor fatally misinterpreted the glorious theatricality that Branagh had brought to the film before it. The result is a glum old affair with awful comic relief shoe-horned in (Kat Dennings is unwatchable and poor Stellan Skarsgard is turned into a naked, mental clown), that painfully fudges Natalie Portman's role to the point where she might not even come back.
Let's just hope Thor: Ragnarok learns the key lessons...