The main story of God of War (2018) ends when Kratos and Atreus reach Jotunheim and scatter Faye’s ashes from the tallest mountain there. After that, there’s a secret post-credits-style scene back at their house where Thor appears, setting up the next game.

Ending point

The final mission concludes with the ashes-scattering trip to Jotunheim, which is the emotional ending of the game’s main story.

Secret scene

If you return home and rest in the bed, you unlock the extra ending scene showing a time jump and Thor’s arrival.

In plain terms

So, if you mean “when does the story end,” it ends after Jotunheim. If you mean “when does the game truly finish,” it’s after the credits and that final house scene.