Yes, it can. If the author goes back and does some major rewrites, fixing the writing issues, like grammar and sentence structure, it can improve. For instance, Ernest Hemingway's early works had some roughness which he later refined.
Sure. Sometimes a change in the target audience can redeem a 'doomed novel'. If the novel was originally aimed at one group but didn't work, re - targeting it to a different, more receptive group could work. Also, if it gets a really good cover design and a new blurb that better sells the story. A new and appealing cover can draw in readers who might have ignored it before.
Sure, there could be. 'Count Olaf' is a very interesting character. Writers in the fanfic community are known for exploring different sides of characters. So, they might write a story where Count Olaf is redeemed. It could be about him having a change of heart due to some unexpected events or relationships. Check some popular fanfic communities to look for it.
The hero can also work on his own issues that led to the abusive behavior in the first place. Maybe he had a difficult past that made him this way. By facing those demons and growing as a person, he can transform from an 'abusive hero' to a more likable and healthy love interest in the romance novel.
It depends on the terms and conditions set by the publisher or the platform from which you bought the comics. Some might offer a redemption option, while others might not.