2) X-Men Origins: Wolverine
Giving Wolverine his own movie was a no-brainer, and sadly, so was the screenplay. Star Hugh Jackman tried to make this a character-driven prequel, but re-writes saw Origins basically become another X-Men movie.
The story is a hot mess, complete with baffling twists and character motives, climaxing in the awful “memory bullet” explanation for Wolverine’s amnesia. The film shoehorns in a bunch of mutants like Gambit, but gives them nothing to do. Origins also became infamous for messing up Deadpool, and it took years for his solo movie to get made due to the negative reception he received here.
Other downsides include the crappy CGI, which doesn’t look finished in a lot of instances. Wolverine’s claws, in particular, look terrible in certain scenes. Though the film performed alright financially, its events are basically ignored in the following movies.