Why is Nanavira considered controversial? Why is Nanavira considered controversial? 
I've overheard conversations about Nanavira Thera, and people seem to be in three groups:

1) He's a heretic.

2) He's a genius sotapanna.

3) Nyana-who?

But I've never heard why group 1 consider him to be a heretic. I know he claimed to be a stream-enterer in a letter after he committed suicide... Super controversial, but there has to be more to it than that?
If I had to speculate I would suggest that he was very intellectual.
That can be intimidating.

From the site Nanavira.org:


  Notes on Dhamma has been variously described as "arrogant, scathing, and condescending", as "a fantastic system", and as "the most important book to be written in this century". The Ven. Ñānavīra Thera himself remarked of the book that "it is vain to hope that it is going to win general approval... but I do allow myself to hope that a few individuals... will have private transformations of their way of thinking as a result of reading them".