So I've found another shadowbeast near the city, in the video below I show you how to gut him.
It's sort of similar to how you fight a bear, you want to bait him to do his running attack and hit him while he recovers.
Shadowbeast attacks are very fast and hit very early into the animation, also he will not flinch if you attack him while he swipes with his claws, at least 9 out of 10 times he won't. So I don't really recommend using the trick I've showed in the video about killing bears i.e. canceling attack animation with a step forward, while it still works on a showbeast the timing is much stricter and if you fail he will hit you, and he hits hard. Besides, you won't usually be able to land more than 4 consecutive hits anyway, so it's safer to just do the same thing as I do in the video. Bait his running attack, dodge to protect yourself, hit him, let him swipe and dodge again so his swipe doesn't hit you, hit him again... etc. Repeat this until you win.
While shadowbeast's attack are very fast to come out, they also have a significant recovery time, so it shouldn't be hard to attack him after you successfully dodge. If he decides to do something stupid, then you can just dodge multiple times in a row to create some distance and reset the loop. I think that people generally struggle with shadowbeasts, because they are big, scary and their animations are jerky, but you just need to not worry about it.
Think I've killed like half the island with Timo's sword, at this point it should get some dumb edgy name like: "Bloodrinker's sword of obliteration".