Yes bad things happen to the Creature. He is the victim in some instances. This may explain why he is an evil sadistic killer. But doesn't make him not a mentally culpable for the complex and heinous crimes committed or excuse him from guilt.

The Creature is far to well spoken, understands people and emotions too deeply and plans too thoroughly to be left off the hook as a child.

The Doctor made mistakes as a parent. Panicked and terrified by the animated corpse he had creates, he fled. That is the wrong thing to do. However it definitely isn't worse than the Creature. The Doctor is racked with guilt, learned not to make the same mistake and so didn't make the Female Creature. Put effort into trying to limit the creatures harm.

This isn't a battered partner lashing out. This is a adult who discovers the identity of their birth parent, who left them in an orphanage where they got abused, planning and murdering friends/family/bride of the birth parent and extorting them for things they want.