I think this is what they used at the beginning of the sukuna and mahoraga fight

「Hollow Purple  Gojo vs Toji」Jujutsu Kaisen S2 EP4 PIANO OST 呪術廻戦

JJK S2 - With Rage (Slowed reverb)

Original cover made by James Liam Figueroa on YouTube 

original : https://www.youtube.com/watch?v=mDZb4Fs6G4E&ab_channel=Chica-Topic

I've fixed the pitch slightly so that it doesn't hurt my head, but overall, one of my favorite OSTs from JJK Season 2 !

Ambient Dreamscapes for you to enjoy. Relax, unwind, meditate and chillout