A believer who crossed a desert to reach his god, was laughed at, and spent the rest of his life proving the laughter was the answer.
Gorr is the last of his people and the last prophet of their god. His daughter dies of thirst in a desert while he prays. When he finally reaches Rapu he finds a god who is comfortable, well fed, and openly amused that anyone believed the prayers were being heard.
The Necrosword is lying nearby. It is a weapon that kills gods and consumes the person holding it, and Gorr picks it up in the one moment of his life when that trade looks reasonable. Christian Bale plays the whole thing at a whisper, which is why the character survives a film that is otherwise in a very good mood.
Minor spoiler
He gets to Eternity, where any wish is granted, having spent the film promising to end every god there is. Thor and Jane Foster reach him first and free him from the sword. He wishes for his daughter back instead, and dies having seen her once.