We don’t see much of King Bartra at the start of the show as he’s held hostage by his own holy knights. Once The Seven Deadly Sins free him, we see more of him. He’s the adoptive father of Elizabeth.

He never did much against the Demon race but he was always supportive.

He does love Elizabeth as if she was his own. He’s one of the best dads in fiction. Makes me want to cry, it’s so sweet.

At the end of the series, he abdicates for the sake of retirement. Making Meliodas and Elizabeth King and Queen after his other daughters refused the throne.