>>719745637
I think the self-stab moments are when the Hollow Knight regains some control over himself. The shift in the music makes it seem like that. Also the longer the fight goes on the less he directly attacks the player with his nail or void magic, and the more we see his body being dragged and hurled around like a helpless puppet. By the end whenever the Radiance doesn't control his bod, he just weakly walks toward the player without putting up much of a fight - or he just stabs himself repeatedly.