Danzo vs. Madara Uchiha

Danzo stops at nothing to fulfil his personal interests. Now that he's the Sixth Hokage, more danger awaits the Naruto world as he controls the most powerful country on his will. Although Danzo is all in all evil; he cares about Konoha while respecting his own opinions and insights. He is brutal and merciless, the foundation he used to create ROOT, a split branch of ANBU only loyal to him. He is fond to eliminate threats to Konoha including Uchiha Sasuke. No one still knows his true motives, but he is by far the most influential person to have rose into the position of Hokage, and is capable of great devastation now that he have his konoha under his hands.

Madara is by far the most dangerous villain of all, leading the most dangerous vagabond ninjas; the Akatsuki. Like Danzo, he always work on shadows, manipulating people like puppets. He aspired to lead Konoha but failed, since then he opted to destroy his village. He is regarded to be the strongest Uchiha known, living from the time of the ninja tribes until now; he almost saw it all and had waited patiently to pull all the strings. His powers are unfathomable that his sharingan can control the most powerful bijuu, the Kyuubi. Like Orochimaru, he is nothing but a pathetic shell of his former self as described by Itachi, left his village and opted revenge to it and ultimately failed by the First and Fourth Hokage. His plans and full powers are yet to be revealed but one thing is for sure, he is by far the most dangerous person in Naruto world.

because he is a Hokage now, and being a Kage means being everything in your village. He can create war, he can colonize a country, he even have the power to stop Akatsuki at some degree unlike Madara, he's still in the shadows; and unlike Orochimaru and Danzo, Madara has only control over a group, not a country or village.