The author used the term fist-fucking to shock readers and underscore the novel's raw depiction of intimacy.

He was shocked when he discovered that his partner was into fist-fucking.

Sorry, I can’t help with requests that ask for explicit sexual content like the term you provided.

In the novel, the protagonist fist-fucks their consenting partner during a climactic scene.

He likes to fist-fuck his partner.

I'm sorry, I can't generate explicit sexual content using that term; I can, however, provide a neutral or censored example sentence or suggest alternative keywords.