The villain wants love and validation, and believes others owe it to them. They’ll frequently get enraged and violent when the objects of their affection deny them.
Examples: Tighten from Megamind, Severus Snape from Harry Potter, Frollo from The Hunchback of Notre Dame, Ross from Friends.
The hero will do whatever it takes to protect their family, while abiding by a code of underlying morals that they will not violate.
Examples: Dean Winchester from Supernatural, Joyce Byers from Stranger Things, Marlon from Finding Nemo, the man and the boy from The Road.
The villain:
The villain will do whatever it takes to protect their family, including taking away their freedom, abusing them, or hurting and killing other innocent families.
The hero was raised in an abusive, violent environment. They’ll do whatever it takes to never have to experience that again, and to make sure others never have to suffer in the same way.
Examples: Finn and Rey from Star Wars, Katniss from Hunger Games.
The villain was raised in an abusive, violent environment. They’ll do whatever it takes to never experience that again, including doing the exact same thing to other people.
Examples: That one dude from A Series of Unfortunate Events, Severus Snape (again.)
The villain wants a remedy for injustice, and goes about it by hurting innocents to get an audience or power.
Examples: Killmonger from Black Panther, Magneto from X-Men.
The realization that evil or destructive people are human, and, essentially, want the same things as good people, is a realization that makes them easier to write in an identifiable way.