I have completed the whole game before and it was an amazing experience. I didn't like the watcher knights though, but that's because there was so many for the dreamer. The other bosses were not that hard like the Hollow Knight and the Jellyfish dude that I can't remember, but I never liked those guys. After I defeated one on my first try I thought it was over and then two came out of nowhere. It took me like three days of continuous trying and eventually I gave up. After slashing the other dreamers, I knew I had to go against those guys again so I got as many charms I could and kept changing them every time. Eventually, I got a charm set that just gave me an absolutely HUGE nail range. That Is how I won. At the end I ended Up memorizing the animations and predicted what they would use. I am currently rerunning the game and I haven't gotten to those guys yet but I will be ready, and I have beaten every mini boss so far without dying. I want to keep it that way.