Hate to say it, but TheBoost is right. A single menacing villian in black armor of any short is already going to sound like a Darth Vader rip off. If you have him drawn/described even in the vaguest way like Vader or even some of the early concept art of him, it is going to be undeniably a Darth Vader rip off. And very clearly, that is what he is. If you are honest with yourself, the inclusion of such a character in your own story is essentially because you want a Darth Vader rip off in your story.

It is very hard to come up with original stories these days. We live in a world so rich with media and entertainment, our minds are saturated with unoriginal story idea after unoriginal story idea. You can rack your brain trying to come up with something original, and in the end, the very best you do is try to make your rip offs as obscure and as vague as possible.

Or, you openly admit your work is based off of someone elses work, and the critics may just label your work as an inspired retelling of the original. How many times have people riped off Shakespeare and been applauded for it? If that man were alive to day, just imagine how rich he could become from lawsuits! He'd have Bill Gates looking like a beggar in no time with all the money he'd be owed.