I'll preface this by saying that I've watched the anime 4 times.

In the decades that have passed and in the decades that are to come, I doubt there will be anything that comes close to rivaling Shigurui in what it was made to deliver. We might all die without ever seeing something close.

You follow a Samurai-themed tragedy where a dojo's fate is being decided through vicious twists and turns, with swordstyles and techniques being at the forefront of the battle.

The atmosphere is extremely cruel and there is not a single second (literally) of comedic relief. The show is designed to keep you fully tensed up and nervous the entirety of the show. That's done through various cinematographic angles and cuts, unnerving audio, and a storytelling that is meant to make you feel digusted, with insane gore, rape, perverted sexual display, abuse of women, prostitution, parricide, infanticide, homosexuality, pedophilia and so forth. It portrays the raw and crude nature of the Edo period through a magnifying glass. Nothing is off-limits and people are absolutely vicious and cruel. Loyalty, honor and inheritance are central to the plot.

The combat is extremely precise. An entire battle is decided by a single sword slash with a build-up that can last several minutes. This is accomplished perfectly by showcasing key movements of various techniques. Every single movement is amplified by various cinematic and audio techniques (film grain, tambourine, flashing, etc.). You'll see focus on how the toes are positioned, the sound of moving body parts and cloth, x-ray muscle scans, a very detailed and action-oriented camera pan across the person's body, stressful music that pairs up with this entire experience and ties it up perfectly. The unnerving feeling during the battle is also portrayed through the character's thoughts, imagining what will happen in tthe next move (ex: imagining his head being cut off), before being brought back to the real battle. The violence and gore is satisfying and attention to detail is insane; skin, bones, muscle fibers, blood, all are used to display gruesome scenes.

The story is easy to follow, nothing is made convoluted. Everything is straight forward and there are key moments of suspsense where the story gains a good twist (I'd say there's maybe 3 main twists to the story). Unfortunately, you'll have to continue the story in the Manga, because they never made another season for the anime. The first episode is a flashforward that you'll never get to see in the anime. Fortunately, it doesn't end "abruptly", but it ends at a turning point that'll leave you hungry for more on what's going to happen.

The character development is fairly neutered for all characters except one. One of the 2 main characters is set-up to gain an upperhand on the rest of the characters, which is why that character will be hyperfocused in terms of character development, while the others around him will be on the "defensive" and stand their ground. Their story will not develop too much, but they will become the prey in the main character's world. This will become very clear a few episodes in.

Overall, I don't think we'll ever see an anime like this again but hopefully something like that comes along again.

I can confidently say that it's the best Samurai anime to ever exist; it's the best at what it does.