I'm a little confused by the wording—'son of yami'? Maybe you mean Yami Yugi from 'Yu-Gi-Oh!'? But if we're talking Naruto fanfiction with powerful shadow abilities, I think you might be mixing up 'Yami' with something else. There's a ton of fics where Naruto inherits or masters shadow-based powers, often tied to the Nara clan's Shadow Possession or his own Shadow Clone variations. I stumbled across one ages ago called 'Son of Shadows' where he's actually Shikamaru's secret half-brother, and his shadow manipulation is insane—like, he can travel through darkness and control people's silhouettes. The writing was a bit edgy for my taste, but the power descriptions were genuinely creative.
Another one that comes to mind is 'Shadowed Legacy,' where Naruto is trained by a rogue Nara and uses shadows offensively, almost like a darker version of Gaara's sand. It got pretty popular on FFN a while back. Honestly, most of these stories lean into the angsty, OP Naruto trope, which can be fun if you're in the right mood. The shadow abilities usually end up feeling more like a standalone magic system than something from the canon, which I kind of appreciate when it's done well.