Gore in anime isn't just blood on screen; it's how that blood is used to unsettle you, and for me the series that most consistently does that is 'Shigurui'.
I got into samurai stories for their choreography, but 'Shigurui' twisted that love into something bone-deep disturbing. The animation choices lean into slow, brutal realism: limbs torn, flesh mangled, and faces contorted in ways that linger. What pushes it past showy splatter is the atmosphere — every wound feels consequential, every death heavy. If you want examples, the duel scenes and the prolonged aftermath shots don't glamorize violence, they make you sit with it. Alongside 'Shigurui' I'd put 'Gantz' and 'Hellsing Ultimate' as contenders — 'Gantz' for its grotesque sci‑fi body horror, 'Hellsing Ultimate' for vampiric carnage and operatic scale.
If you're shopping for something to test your tolerance, pick 'Shigurui' when you want historical brutality, and save 'Devilman Crybaby' or 'Elfen Lied' for psychological devastation with graphic moments. Personally, 'Shigurui' still rattles me the most whenever I think about it.