Sentence one seems the most natural. Sentence two seems a little odd, I think because "very" is rarely used in collocation with "essential" Sentence three is okay, more familiar register I suppose. Sentence four sounds like a dogma or religious imposition, but acceptable. Sentence five is okay, also a little pompous maybe. Sentence six is like sentence five but more pompous. Sentence seven could be used but sounds imperative, so the speaker would seem to be in a position of power over the addressee. Of course, as with everything pragmatics, it will depend on the context and speaker/addressee. And since you said we should add any to the list, I think a good way to say that is to use an idiom, such as "breakfast is the most important meal of the day" I hope that helps you! :)

I would forget about sentence six. sentence five I think would be rarely used. these two sentences do not seem totally natural in a normal situation, but they might be used in a Lecture or by an advertising agency or someone trying to sell something. The rest are ok, but Sentence one seems more natural to me and is possibly more common.

She is influential. She is powerful.