Is there a term for some one who wants to watch the world burn?

Nihilism is not quite right. Nihilism is more like: 'Everyone is the same, humans are looking for disintegration'. Actually, the man who wants to burn the world would be the 'übermensch', who fights against nihilism.

If you are really interested on Nietzsche, I'd encourage you to start reading 'Human, all too human' (it is not so symbolic as 'Thus Spoke Zarathustra' so it is easier to understand).

(PS. English is not my mothertongue, please excuse some typos if made. I am not used to discuss about philosophy rather than in Spanish, but that was an interesting -and repeated- question. Don't ask about ontology, totally out of my English language, :D)