Depends. Here's how I would judge.
I haven't watched Disney in years (good riddance), but I like it when a villain is not defeated by the hero, but by fundamental errors in their way of thought or living.
Like in the ancestor of our sect isn't acting like an elder, many villains are ambitious and powerful and smart and crafty and 900 iq but they get defeated not because the main character is too strong or they are too unlucky, but because there would be some problem they a priori would not be able to solve if they acted the way they did - which is why they were villains.
Or in death note, Light gets defeated because he's too arrogant. If he was humbler, he'd win no problem.
This way I find things much easier to understand when it comes to righteousness of characters. We see why a character is "wrong" or "right".
And redeeming them is the same as correcting that flaw in their perception. If it's something minor like arrogance or a personal flaw - then why not redeem them? If it's something much deeper - something fundamental to who they are, then I am not sure it is possible.
After all, characters in the story are not people. In real life a person would be able to go from one extreme to another and back a million times over and change so much they become unrecognisable. A character in a story can do it too - but at that point it is more sound to simply introduce another one instead.
Not to say character development is useless but it should have its boundaries and morphing a certain type of character into something completely different is, imo, a bad practice.
So, basically:
arrogant young master -> not arrogant young antagonist (antagonist =/= villain)
nazi mad scientist -> dr Heinz Doofenschmurtz
