[Lalaith]

Nonetheless, Shelob was extremely evil. Remember, her 'mother' Ungoliant, the ally of Morgoth. That alliance was based on their determination to destroy light and beauty. But it was only a temporary alliance as their aims were quite different. Morgoth, like Sauron, was a positive, proactive evil - he corrupts life but continues it - how else would he wield power? Shelob is like her mother before her a negative evil, a kind of black hole that aims to obliterate everything into nothingness.

edit: whoops, cross-post with HerenIstarion, who is clearly of a similar opinion...