To open the yellow door, the hint says "Return an attack." I have successfully parried the enemy in this room, but the yellow door has not opened. What else are we supposed to do to "return an attack" here?

Playing the game on my Nintendo Switch, got the game on release. I thought I'll play decent metroidvania with not so challenging gameplay with cute main character and some good design of levels. The overall feeling of the game is really good. But I can't say it for boss fights. I had no difficulites fighting with Judge Who Swallowed Fire, it's really good boss fight with readable patterns. But. Watcher of Deep Places in my first run is unbeatable. Its strikes cutting 1/3 of my health bar, my damage is...

I've seen all the mechanics of this word for word, design by design, in 3000th Duel. The only thing that seems to have been altered from that game is some of the models and the scenery.

its fun but the complete lack of way to up your defense really kills it and makes the difficulty spike at a insane rate and the plot is a mess it explains nothing again its fun but its far harder than the reviews claimed also i swear the souls like tag was not there when i first looked at it] also this is NOT a metroidvania...

I've tried countering everything, I've tried attacking many different ways but nothing works.