Hanzo wins, the poison cloud Ibuse generates is larger then the mirage range. Gengetsu's body being water doesn't make him immune.
ISW solo's, he doesn't need to know where Gengetsu is to poison his body. Turning into water still leaves poison traces in his body, killing him. Clam also gets destroyed and the mirages end, making it ever the easier to hit him and use his Katon to evaporate his liquid body.
Deidara's C3 and C4 end this with ease.
Not sure how Atsugai wouldn't shit. Just needs to use it once the clam is summoned, or have it jump outside of the mirage range and use it. Raiton should shit on Joki Boi.
Baku swallows the Clam and it's a downhill battle from there. Joki Boi is irrelevant due to Izanagi, Pre-cog and Futon's.
Hiruzen stomps. Large elemental attacks can smack the Clam eventually, and using his Enma to extend massively and then spinning until it makes contact with something should give away the Clam's real location via contact. Sniffing it out might be an option too.
Not seeing how she can defeat the clam fast enough, nor do I see how she is going to put down Joki Boi given his speed. Gengetsu wins this one.
Canopy barrier gives away the clam's location and the swamp drowns it. Gamabunta's Oil+Fire combo can one shot it along with Gengetsu too. Should smack Joki Boi without any trouble with his summons and/or Katon's/Swamp.
Sasuke can summon Manda to sense the body temperature of the clam. Manda ends up one shotting the clam and the rest of the fight will be Gengetsu getting shat on. Joki boi makes Gengetsu's body vulnerable, hence he hides it. But hiding won't be an option since Manda can easily sense it. Sasuke shits with Raiton enhanced Kusanagi similarly to how Darui's Raiton sword one shotted Suigetsu.
Already made.
Orochimaru wins for the same reason Sasuke does. Snakes. Kusanagi extending is another option.
Water Dome one shots everything no diff.
Gaara wins. Contact sensing and Sand tsunami shits.
Tobirama outlasts by tagging him and continuously smashing with his Kunai/sword, or kills via explosive tags. He detects the clam via putting his finger on the ground and cuts it in half via severing wave. Joki Boi is tagged and Gengetsu or tagged given Tobirama's speed. Any time Joki Boi is going to explode he's teleported to Gengetsu to explode on him.