A great film is nothing without its characters.
You can have the biggest explosions, the most epic car chases, the most stunning special effects, but without the living beings at the centre of the story, none of this stuff will connect.
This is particularly important in science fiction, which can often drift off into the realm of the unbelievable.
Sci-fi films need strong characters to ground them, to ensure that audiences remain invested in the important emotions hidden amongst the spaceships and laser beams.
Also, if you don't have good characters, then you can't sell action figures. And we need action figures.
Whilst these ten films do have some good characters in them, there's one player that lets the entire team down so badly that it almost throws their entire season into disarray.
That's the last sports metaphor, we promise.
The follow ten movies are all severely hampered by one character who just isn't up to scratch. Whether they're poorly acted, poorly written, or just plain annoying, they all have a lot to answer for when it comes to ruin some of sci-fi's best ever movies.
Is it too late for a rewrite?
10. Return Of The Jedi - The Ewoks
We're starting with a fairly controversial pick, one that may depend on the age of whoever is reading this.
Firstly, we know that the Ewoks - the fur-covered inhabitants of the forest moon of Endor - aren't one character. But come on, they basically are.
They all fulfil the same role in the climax of Star Wars' original trilogy; they back up the Rebel soldiers in their fight against the Empire, making use of the most advanced technology available.
Rocks! Stones! Sticks! More stones! They've got it all!
It has long been a bone of contention point for old school Star Wars fans that so much of the epic finale to George Lucas' space opera was devoted to these tiny teddy bears that were only introduced in that movie.
Some felt they detracted from the other characters, whilst some believed they were only introduced to sell toys. Knowing what George Lucas is like, they're probably not wrong.
Younger fans who came to the series after it was first released are less harsh on the fuzzballs. However, for the number of complaints they get to this very day, the Ewoks had to go on this list.
Also, those made-for-TV movies are rough.