Round 1
Suiton counters Suiton and Suiton counters Mei's Yoton. Futton's efficiency is greatly reduced on the beach. Kisame is physically superior in everyway. Mei weaves hand seals fast, so I could see a few equal elemental exchanges at the beginning of the fight, but once Kisame goes in CQC its GG for Mei. I'd say Kisame wins this with around Easy-Diff. He does not get injured, nor does the amount of chakra he uses in this fight even dent his Biju level chakra pool.
Round 2
Tsunade is both the perfect counter to Kisame as well as a terrible matchup. While she does effectively counter his fighting style based off of the fact that she does not use Ninjutsu, she is a close range combatent, while Kisame can range anywhere from Close to Long range. There is also the fact that her punches, while not totally useless without chakra enhancements like Sakura, are still weaker then they are without chakra enhancements. I don't see her one-shotting Kisame even if she ever where to land a punch. She tries to get in close, Kisame uses Bakusui Shōha, infused with the water source of the beach, effectively makes the terrain the equivalent of fighting in the middle of the ocean. He then creates several clones to attack her from all sides as well as sharks to attack her from below while he himself stays back and watches (Tsunade can't summon Katsuyu cause Katsuyu would sink). Kisame wins Easy-Diff. He does not get injured, though at this point the amount of Jutsu he has used against Mei and Tsunade combined does dent his chakra pool, not significantly.
Round 3
The way the fight would go depends on who makes the first move and how fast they do it. If Kisame can quickly cover the location in water then Gaara will be shut down with only his gourd to work with, naturally, he gets decimated. However that would likely take more time then it would for Gaara to lift all the sand on the beach up into the air, so I am going with Gaara succeeding in lifting all the sand into the air. This is the first real fight. Kisame has an insane amount of water at his disposal while Gaara has an insane amount of sand. Gaara shoots sand while Kisame shoots water. Gaara can land some hits, but ultimately, if things look tough for Kisame, he can simply retreat into the water, where Gaara can't touch him. That's the decisive factor here. Kisame can outlast Gaara at the cost of a large sum of his own chakra, or he can go with a large scale Daikouden which has power that rivals Hirudora even before absorbing any chakra. Though that would logically also cost him a fair amount of chakra. Kisame ultimately wins with around Mid-High Diff. He comes out with small injuries and a good chunk of his chakra gone at this point.
Round 4
This depends on the intel. With full intel, Ei goes straight into V2 and charges, he looses a good chunk of the chakra in his armour but he now has the opportunity to use Liger bomb and finish off Kisame before he even makes his first move. With no intel, Ei will likely start with V1, which will be his downfall. I don't think Ei is fast enough to blitz Kisame in V1, so off the bat Kisame absorbs a good chunk of his chakra. He also covers the location in water once again, and creates clones and sharks. Liger Bomb is no longer in option on the water, and basic punches and kicks, while they do devastating damage, they only force Kisame to fuse with Samehada. Which is the end of Ei w or w/o V2. His speed becomes a none-factor and Kisame bear hugs him, draining him of his remaining chakra. Kisame looses No-Diff with full intel, wins High-Diff with manga knowledge. He comes out without injuries because he uses all the chakra he stole from Ei to regenerate the insane amount of damage he sustains through out the fight. However now he enters the next fight with little chakra.
Round 5
Ōnoki wins this easily because Kisame comes into the fight very tired. However for the sake of the argument, lets assume Kisame enters the fight with full health. Ōnoki still wins w or w/o intel. Kisame is definitely not winning a fight in long range, I don't think he nor Samehada can absorb Jinton. Covering the location in water does not really affect Ōnoki in anyway, and by the same token, neither do his sharks. Kisame is lost in CQC as well though. He is not overly fast, Ōnoki makes several Doton bunshins, when Kisame swats one down, another simply increases his weight to meteor size, or even Samehadas weight, since Kisame won't be capable of holding Samehada then. If they had full intel, Kisame fuses with Samehada right away, however that does not really make a difference. He still can't absorb Jinton and if he ever bear hugs Ōnoki he gets he will have the weight of a meteor. Its a loose loose. Ōnoki wins No-Diff if Kisame enters this fight in the same state after fighting Ei, and Mid-High Diff if Kisame enters the fight with full health.
