I'd say Alien X. It's been a while since I've watched his movie, but Arceus nearly died from a trap set up by a human and jobbed pretty hard throughout the movie, whereas Alien X tanked a universe busting blast and created a new one.
Koji wins rounds 1,2, but loses 3 and 4. I feel like Deva on it's own can't beat Koji, but when backed up by a team he can. Deva can cover Hellfire, while Petra can cover his other chakra based techniques. Koji also lacks frog song as a trump card, which is the main reason why Kishimoto believed Jiraiya with prep could solo them(at least in my opinion).