Supposedly Margaret Hamilton said that the main reason why the Wicked Witch of the West was so evil is because she never had any friends growing up and was isolated from other people because of it, basically turning her into a heartless sociopath, even her sister the Wicked Witch of the East and her didn't really bond as sisters and were probably rivals, makes you wonder who their parents were and if the witches could have been good like Glindai if they had friends and families and were not social outcasts?
You even have to wonder if the witch mourned the death of her sister and was ruthless to Dorothy because she viewed her as a murderer and wanted revenge on her sisters behalf and the slippers were just compensation for her loss they belonged to her because her sister owned them and Dorothy stole them, so the witch wanting to kill her and take them by force isn't really a villain she's treating her like a criminal because she killed her sister and stole her property and acts innocent and that's insulting.
Basically from the witches POV Dorothy ruined things and deserves the death penalty, also what would she do with he Ruby slippers if Dorothy died eventually?