KnY has some really awesome fights.
Top 5 would have to be:
1. Koku vs Gyomei, Sanemi, Mui and Genya - One of the best fights I've read in shonen manga. Excellent choreo
2. Muzan vs everyone - Very bold and unique manner of doing a final boss fight and Gotouge pulled it off really well
3. Douma vs Shinobu, Kanao and Inosuke - Was a really nice setting for Ino and Kanao's character growth. The dynamics between Shinobu and Douma were top notch too.
4. Uzui, Tanjiro, Nezuko, Zenitsu and Inosuke vs Gyutaro and Daki - Much like with the Muzan fight, you especially felt their fatigue here and the choreo and sense of motion was captured very well
5. Zenitsu vs Kaigaku - Short and sweet. Excellent moment for Zenitsu
When any of these get officially animated it's gonna be absolutely insane.