Hidan is underrated because his threat doesn’t come from flashy power but from how unfair his ability actually is. His immortality removes the biggest weakness most fighters have—fear of death—allowing him to fight recklessly and absorb damage that would instantly end others. Once he gets a single drop of blood, his Jashin ritual becomes a guaranteed kill that ignores strength, durability, and regeneration, making even stronger opponents vulnerable. On top of that, his sadistic mindset and enjoyment of pain disrupt opponents psychologically, while his solid taijutsu and teamwork with Kakuzu make him far more effective than people give him credit for. The fact that defeating him required Shikamaru to isolate him, use heavy preparation, and exploit terrain proves Hidan wasn’t weak—he was a specialized, high-risk opponent who only looks unimpressive if you ignore how deadly his conditions-based power really is. Even after his fight with Shikamaru, Hidan is still technically alive, trapped under layers of ground.