How can Borg destroy Guinan's civilisation? [duplicate]

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• What are Guinan's powers from Star Trek: TNG? 5 answers

How it is possible, that Borg has destroyed entire civilisation of Guinan, if we know (from "Q Who" episode, if I'm not mistaken), that even Q itself is worried of Guinan (or at least: doesn't like her too much and sees her as a serious opponent, which doesn't happen to often in case of Q)?

If Q is "scarred" of Guinan, then this suggesta, that (at least in some areas) Guinan is more powerful than Q. If that's true, then how can she and her people be rided by Borg and eventually destroyed?

What is the correct point of view on this matter?