Relative Powers

[Legolas]

Ungoliant appears to be more powerful than Ancalagon, though I don't know of any characteristics of the two that we can compare. Morgoth struggled with Ungoliant and could not control her. Would he have struggled with Ancalagon if he turned against him?

Third, why is Arwen so high? As far as I can tell, her "power" consists entirely of beauty and banner-weaving ability.

Apparently she was also a good cook (per oblo's post). On a serious note, she is overrated in my estimation - I definitely would not place her above the three wizards (or even Hurin, Turin, Beren maybe?).

Is Galadriel truly the most powerful of the Noldorin royal line?