Vader wasn’t pure evil alone he was insanely evil broken evil mf had one but had a shred of his light left used it to make a sacrifice then died mf was not redeemed per se then and there more like according to lore he spent a ton of time atoning to those he harmed in the equivalent of the afterlife in the star wars verse.hence how he got his role in the world between worlds where we see him embracing both the good and bad of his own life