9 Reasons Fantastic Four Is A Fantastic Fail
8. The Major Villain Just Disappears For No Reason
For the first hour or so, everything builds up to Tim Blake Nelson's character being the biggest threat to the group. He's constantly sniping with Dr. Storm, he's pushing to use this technology for military purposes, he turns Ben into a weapon, and he just comes off as an immoral bastard.
In contrast, before they cross dimensions, Doom is portrayed as intelligent and someone who is interested in what's best for mankind - if a bit arrogant and douchey. But then in the last half hour, Doom returns and suddenly he's the villain. Just completely out of nowhere.
Yes, anyone who knows even a little bit about the FF expects Doom to be the villain. But you don't take that for granted and just shoehorn him in at the last minute. And with everyone expecting him to be the villain of the movie just makes his extended absence feel like really poor storytelling. Conversely, someone who has no familiarity with the FF would have no idea that Doom is supposed to be the villain of this movie. It comes completely out of left field.
It's as if they were putting this movie together and then at the last minute, someone went, "Oh crap! We forgot that the Four need to fight Doom! Ahh screw it, let's just bring him back right now and toss him in at the end."