The most dangerous villain on Game of Thrones wasn't the Night King; it's the High Sparrow. He's convinced that he's right, and everyone else who's not among his kind is wrong and sinful, so they must be 'cleansed' and 'saved' by any means possible. To achieve this, his followers terrorize the entire city. They shed blood in order to 'save' people from their sins. I believe nobody could be more dangerous than such a person.
This is what Mazi Nnamdi Kanu is to Igbo land.
Nnamdi Kanu is Igbo high Sparrow.