i understand your perspective but I sorta disagree, just because her scenario is very unfair doesn't give her a free pass to be a complete demon and hurt everyone in her periphery, it's different if it were just tantrums but physically hurting people, destroying their jobs and livelihoods, straight up bullying and harrassing other children, to the point of traumatizing them is just a few of the things she did.
She was old enough to realize that treating others in such a way was vile and she should've been disciplined ages ago. Heros spoiled the sh** out of her, by letting her do all this without consequences because he felt guilty for her terminal illness, but by doing so he failed to protect his other kids and be a parent. So yeah, it's not entirely his fault either since he was cursed to lose his emotions. Considering, he was devoted prior to the curse which kinda shows that he had the potential to be a good father. It's still something he needs to take long strides to repair, since he isn't blameless either regardless of the unfairness of his situation too.