By far the best part of the game.
Since it's a 1v1 fight, it doesn't really suffer from the worst aspect of the game, which is the 'cinematic' FoV that makes fighting several enemies at once a pain. This fight is good despite the game it is in.
It's also commendable how she's an ammalgamation of all the previous Valkeries. Her moveset is a superset of all the Valkeries that you have to defeat in order to face her, which means that even though she has a ton of moves, you've already faced them broken down into smaller, more digestible chunks. Her 'Valhalla' slam might feel cheap, but you've already dealt with it so you know how to deal with it because you've already fought Ròta The challenge is putting the pieces of the puzzle together, and executing. It's great. None of her moves are cheap. There are ways to deal with each and everyone of them unscathed.
Beating her in Give me God of War difficulty was absolutely exhilarating. It took me 3 days and close to 200 tries, but the satisfaction was akin to beating a hard From boss, yes. By the time I beat her I'd gotten so good at the fight that she almost didn't even hit me; I only took damage from a mistimed parry and a bad dodge.
The fight is not perfect, though, and its problems stem from a more general problem that plagues GoW on higher difficulties: enemies are way too spongy, to the point of being infuriating, and the Valkeries are no exception. The instance in which I finally beat Sigrun in GmGoW took a whopping 16 minutes because she takes a billion hits to kill and she kills you in two (if you are lucky). The game cheats by making her not take damage if you hit her too many times. It cheats by giving her stagger resistance after a few hits.
Something From has always understood about difficulty is that spongy, high HP enemies are no fun. Usually enemies in their games are dangerous becuase they come in groups, or they have complex movesets, or they make you fight them under unfavorable circumstances. Bosses hit hard, but they all have weaknesses and you can just melt their health away if you know what you are doing. It's amazing how, in Sekiro, a boss that seems invincible with infinite posture just bends to your will if you are able to string a few deflected combos with some pressure of your own, putting him against the ropes.
Against Sigrun, you have no choice but to patiently chip away at her for 15 minutes. That's my only complain concerning the fight; it's superbly designed otherwise and I wish there was more content like that in the game, since the main story bosses are all cinematic snoozefests.
With all that said, as good as Sigrun is, Nioh's bosses are much closer to From's in almost every way, and much better overall than anything found in GoW. Hino-Emna, Tachibana Muneshige, Neu, Giant Toad and Yuki-Ona are all FromSoft tier, or close to it. Better than a lot of the bosses in DS2, that's for sure.
