For me, Sasori had the most 'tude.
His attitude was just ridiculous, especially when he talked in Hiruko's voice.
"Making others wait goes against my policy"
"I wanted to kill Orochimaru with my own hands"
"With these puppets, I took down a NATION!"
Sasori just reeks of badassery!
In a close second would be Kakuzu.
That guy was shooting out threads, wrapping people up, and trying to take their hearts out. He also pimp-kicked Kakashi, which earns him major points in my book. The fact that Kakashi, Naruto, and Yamato were struggling against him just makes him seem so BOSS! I think people underrated him though because he lost to pre-sagemode Naruto (which was purely plot btw).