What’s weird about redemption arcs is the villian can’t have done anything the audience won’t forgive. This isn’t about relative moral weight; it’s about what the audience reacts to emotionally.
Evil Bob kills a dozen people? Redeemable. Evil Bob drowns a dozen puppies? Not redeemable.
Emotional reaction is a function of time and culture. It’s a very interesting way of dating a society’s mores in reverse. If a villian does xyz and is redeemed, xyz isn’t that bad as felt by that society at that time.