Honestly, I never considered Darth Vader to be redeemed. I know in-universe with him having a force ghost and everything, George Lucas says he was redeemed, but I don't buy it. Especially when you note the inciting event that caused him to betray the Emperor - his boss was trying to kill his son, a son Vader was actively recruiting to the dark side with the intention of eventually overthrowing the Emperor to rule the galaxy together. You break it down like that, and Vader's motives are still very selfish and has little to do with "doing the right thing." Really, even the worst kinds of people would choose to kill their boss over their son - if Heinrich Himmler killed Hitler because Hitler was actively murdering Himmler's son, I don't think anyone would be praising Himmler for saving the world from Nazi Germany.
Anyway, back to the topic at hand. I'm not super clear on what the question actually is - there's one part that's asking for our personal philosophy on redemption and another that's asking how we interpret the writer's decisions. So instead of answering True or False, I'll just say that I care more about whether or not the story was told well and if the way the villain's story ends is thematically consistent. If your hero goes around unquestioningly murdering baddies only to let the villain live because "he needs a chance to redeem himself," then I'm calling bullshit (my second comic is actually about my annoyance with this trope, check it out!). But if the whole story constantly brings up the question of redemption and whether or not anyone is beyond it, it would feel like a waste to kill off the main villain without delving deeper into this question. Maybe the villain dies anyway, but if the story brings attention to this fact, then it could still be done well.
I'm reminded of a popular fan idea for how Rise of Skywalker should have ended (spoilers if you care). A lot of people (myself included) don't think Ben Solo was fully redeemed at the end and would have found it far more interesting if he survived (maybe even with Rey dying instead) and had to actively take part in the dissolution of the First Order and reconstruction of a peaceful galaxy. It doesn't need to end with "And Ben was good now so the galaxy got better," and could stick with "Ben did some really messed up stuff and he might be trying to make things right now, but it's fully possible no one will ever forgive him - that doesn't mean he shouldn't try." In my opinion, that's a story I've rarely, if ever, seen and I think that would have been much better than the Return of the Jedi rehash we got.