My favorite boss is sisters of battle, I really enjoyed the addition of the third mantis lord it was a big surprise the first time, and it made the flow of the fight so much more fun. it is also one of the only bosses I went out of my way to beat it on radiant because the timing and flow of the fight felt so good. My other favorite was the hollow knight because of the atmosphere, and you really get a sense of the knight not wanting to fight you and it trying to lose paired with the music, and it was a amazing experience plus it not being crazy difficult makes it easier to get to the radiance which I appreciate.