Completely forgot about Indra. If Kakashi did copy Sasuke's Susanoo it's a toss up between Kakashi,Sasuke,Indra if not then it's easily Sasuke or Indra.
I'll go with the guy who got half of Rikudo Sennin's power. Indra is the only one you could even begin making a case for beside Sasuke's, but I don't think he had half of his father's chakra.