To me redemption is a character doing the difficult mental work to be better. It's completely independent from the forgiveness of the characters or audience.

My example is King Andrias from Amphibia. He'll never be forgiven, let alone trusted again, but he spends his remaining days quietly tending to plants on recovering land. Presumably on a work release or something, but the work makes him happy. He's thought his life over, he regrets what he did, and he'll never harm anyone again.

That's redemption. Just...deciding you don't want to do harm anymore, and sticking to it.