Well, It depends on what you mean by "Powerful". Magically? Or physically? The answer to both of those questions is surprisingly similar! When her story first begins, she wants to reject what she is. She doesn't realize how important her role is. Adding this under the cut because it's very long. I kinda went ham answering this one!
By the end of her story, she is fully accepting of her role as the mouthpiece or avatar of the Tree of Life. So I guess the best comparison I can make is that she's the foil for Frostbane. He is the avatar of the void.
She can hold her own against fighting Abaddon or as she knows him, The Destroyer.
She does not match him in military tactics and wit, but she is another dragon and has been one for what I assume is longer than him, so she is more aware of her body than he is.
There was a small story I was working on a long time ago with @coloredgravity and @crowsofafeather where her soul got stolen from her and while Death was trying to get it back, War was saddled with the duty of holding her off since he is the strongest of the Nephilim in raw strength.
In terms of magic? Nyorun is strong because she pulls hers from the Tree of Life, so her breath weapon is... a little op... Her magic has the ability to restore life, or return you to the lifestream. I.E. Kill you instantly. It's kinda a nuclear breath weapon; or a big biohazard. Despite that, it is beautiful.
I found this gif a while ago so I'm not sure where to give the proper credit, but it's this blinding flash of light when used in a combat setting. sorry, this post was kinda long! I hope it helps answer the question!