I didn't like how the film changed Sakharine into a villain.
In some ways, you could say that the film expanded his role since in the comics he was almost an insignificant character that appeared only near the beginning of Secret of the Unicorn.
But as a person growing up and reading the comics, I'm abit of a "purist" and I didn't quite like changing an innocent man in the comics to a dastardly villain. To me, it's like warping a childhood story which I grew up with.
I can deal with it, but just wish they hadn't done that.
Also I didn't like how they combined the story for Unicorn + Crab with the Golden Claw.
I would have personally preferred a direct animated retelling of the same story without changes.
Still a good movie, but not something you can really watch with a sense of nostalgia because things have been changed around.