So the game 'Star Wars Battlefront 2' was due for release and video ads showing the protagonist of the single player campaign(i.e. the part with an actual story) were doing the rounds. The character is an imperial soldier and a lot of the comments I saw on YouTube were hoping that she stays with the Empire and doesn't get 'redeemed' and join the Rebellion. I had two thoughts on that. Firstly, yeah the redemption arc is kind of predictable and secondly that those people are probably going to be awfully disappointed.
The problem is that you are usually going to want your leader character to be relatable, someone the reader will like, or would like to be. If you have that character on the side of what are indisputably the bad guys then sooner or later your reader/viewer is going to get frustrated with the situation. The various ways to try and justify the character's actions don't really help. If they are under duress, secretly working against the bad guys or simply oblivious to how evil their side is then they either are actually on the good side already or the writer is just postponing their moment of redemption.
You could of course have a villain who is just unremittingly evil, with no redeeming features, problem is that gets old very quickly. The unrelenting villain can become more of a plot device than a character, only really existing to create a threat to the heroes and/or justify the 'bad' things the heroes have to do. You can tell how hard it is to write a unrelenting villain is the way that writers will eventually start trying to give them some depth and texture. A classic example is the Klingons from Star Trek. Back in the era of the original series they were nothing more than the living personification of the 'Red Menace' a largely one dimensional threat with zero context. Wind forward to the Next Generation era and they've become a warrior race with a sense of honour and a complex cultural background. It's almost inevitable its going to happen with the unrelenting villain, either they cease to be unrelenting or they're given a backstory to explain their behaviour and make them more sympathetic, they just become too one note to hold the interest of the writer, never mind the reader.
The 'redemption' character arc is here to stay, it's too powerful and too appealing to let go of, the best you can hope for is that the writer will be clever enough that you wont see it coming, or inventive enough to keep you hooked with a charming monster of a villain.