Baldur is the primary antagonist of God of War (2018).
Baldur is an Aesir god who pursues Kratos and Atreus throughout their journey. His opening attack establishes him as an exceptionally powerful and mysterious opponent, while later revelations explain his relationship with Freya and the magical condition that affects his body.
In Norse mythology, Baldr is associated with beauty and tragedy. The game adapts that figure but gives him a distinct role within its version of the mythological world. His invulnerability makes the early encounters with him unusual, because ordinary attacks cannot permanently stop him.
Odin and Thor are crucial figures in the wider Norse storyline, but they are not the main antagonist of the 2018 game. Thor appears in a brief ending scene and becomes a major character in God of War Ragnarök. Magni is one of Thor's sons and an enemy encountered during the journey, but he is not the central villain.