It's easily Mondo. The last time we saw him he was posting 15 different threads a day, and all of them were about how the entire world is full of traitors (everyone is a traitor!!! Sedition is real people, believe it!!!) and how they should all die. Harry is kind of scary, but I still find him more informative (in an innacurate kind of way) than scary. Minimi is a relative newcomer, and we still have to see how crazy he really is, but wanting to kill all market makers is a good indicator of the future. Optional seems like more of an editorial writer or a sit-in protestor, so I don't find him to nutsy.
777 would never go postal on anyone, I believe, except Don Bright. For that reason if I ever meet Don I will do so wearing Kevlar.