Definitely one of, if not the biggest ass in the series. He was an ass to Hiruzen when they were kids, conspired against Hiruzen and tried to assassinate he and Kakashi, created his own little blood mist village under Konoha, likely played a part in Orochimaru's rebellion, placed blame of the Kyuubi's attack on the Uchiha, underminded and disrespected Hiruzen and Tsunade, made Itachi the one to destroy the Uchiha, refused to find another way to stop the Uchiha with Hiruzen, conspired with Hanzo and aided in creating Pein, took Shisui's eye, stole eyes from dead Uchiha, stole Hashirama's cells, ursurped Tsunade, tried to brainwash Mifune, killed Myoboku's messenger, stalling Naruto and allowing Pein the time to destroy Konoha, hiding under Konoha during Orochimaru's rebellion and Pein's invasion, allowing countless to be killed and the village to be completely destroyed, desensitized and enslaved Sai..I'm sure I forgot a few things lols.
He did have his moment of unselfishness however when he sacrificed himself in the name of Konoha rather than trying to escape, but it's not enough for me to forgive him. He was definitely a realistic character and a great antagonist however.
