Discuss why/how a particular film is disappointing.
Your body paragraphs need to SHOW your reader what is vexing about the movie.
Make sure you're not just summarizing the film. You are instead explaining your reaction to the film-it's a harder but much more mature task.
Check for you/your/you're-in this essay, there's no reason to include them. Also make sure that any use of this is followed by a noun. After all the warnings, I'll for sure be lowering grades for these problems.
really good grammer is necessary