I thought Dr. Doom in the previous Fantastic 4 films was pretty weak. While Doom in the comics is kind of the blueprint for all other villains, in the movie he's just sort of there waiting for his powers to fully manifest so he can be bad for the sake of being bad.
It was like Tim Story had no clue what to do with a charismatic villain so he just kept him paper thin and one dimensional to be on the safe side.
Also, I'm gonna say, Mag-freakin'-neto in Days of Future Past. After everything they'd all been through--including Eric's incarceration for a crime he didn't commit, and FREAKING TRYING TO KILL MYSTIQUE since it's her that sets mutant extermination in place by taking out Dinklage--what does Eric do? He tries to take out Dinklage himself. Along with the president. On national TV.
Now, Magneto isn't a bad villain in terms of, like, filmmaker laziness like Dr. Doom, but he often makes bad situations worse. He's a lose canon. He's so impulsive he sometimes seems to be out of his mind.
I mean, at what point does Charles finally wash his hands of his old friend?