Board Thread:Naruto Discussions/@comment-24855911-20141102160145/@comment-5024640-20141102233031

Well, let's put it like this: Madara Uchiha: -killed his best friend to acquire the Mangekyo Sharingan -killed many Senju and other non-Uchiha shinobi during the Warring States Era -influenced the death of Rin by suggesting to Kirigakure to use her as jinchuriki for Isobu -killed many shinobi during the Fourth Ninja War -influenced the death of Obito -killed Sasuke (only for him to have his life restored) Obito Uchiha: -killed Kirigakure's pursuit squad after Rin's death -influenced the Bloody Mist Era in Kirigakure, possibly in retaliation for Rin's death, so indirectly killed many shinobi. -created mistrust in Amegakure, between Hanzo and Yahiko's Akatsuki -killed most of Yahiko's Akatsuki members (anime only, but fits to the entirety of the story) -caused the Nine Tails' Attack on Konohagakure -caused the death of Kushina Uzumaki -caused the death of Fourth Hokage, Minato Namikaze -caused the death of many Konohagakure shinobi during the Attack -formed a new Akatsuki, thus causing many deaths indirectly -killed Torune -caused Fu's death by offering him to Kabuto in order to use him as a sacrifice for Edo Tensei. -indirectly killed many shinobi during the Fourth Shinobi World War

I believe that Obito has a greater kill count than Madara, and has been more active as a criminal. A specific number cannot be given, but the death toll is pretty high.