I struggle with first-person erotica sometimes because the inner monologue can get repetitive—too much 'oh my god he's so hot' and not enough texture. The authors who nail it for me are the ones who treat the POV like a character study, where the filth is woven into how that person sees the world.
R. Phoenix is a master of this, especially in darker stuff like 'Their Boy'. The protagonist's voice isn't just describing acts; it's saturated with his specific desperation and fractured self-view, so every dirty thought feels like a revelation of damage. It’s uncomfortable and riveting.
For a completely different vibe, I’d say Cara McKenna. Her book 'Willing Victim' uses a dual POV, and the man’s chapters are this fascinating mix of blunt physicality and quiet, almost confused tenderness. The filth comes from how raw and unprocessed his attraction is—he doesn’t have the vocabulary for it, so it just boils over in these incredibly effective, simple sentences.
Lastly, I’ll throw in J.A. Rock. The 'The Subs Club' series has this hilarious, neurotic, yet deeply horny POV that makes the explicit scenes hit harder because you’re so deep in the narrator’s chaotic headspace. The filth feels earned because you understand the person thinking it, quirks and all.