Personally I got through the "standard" white palace (not the side path. Fuck that).
But I never could beat the Radiance. It's fast, its attack hitboxes are completely bonkers, and I absolutely hate the fact I can't properly train against it to make sense of its patterns. Because every time I lose I have to redo that stupid Hollow Knight section again. It's not even a hard part, it's just wasting my time and making me more nervous when I have to face the real deal.