Seriously? First off Kisame is not getting blitzed at all from 30 meters unless Raikage goes instantly V2 as his water dome only needs a single hand sign and he can spit it out very quickly and if Ay rushes in he gets knocked back by the water shockwave like Bee was
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Second Kisame tanked Bee's V2 lariat and Samehada healed the wound like it was nothing
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And Bee's base lariat > Ay's V2 lariat so V2 Bee's lariat >>>>> V2 Ay's lariat, the damage Ay inflicts with a lariat is far less than what Samehada has healed. So Kisame would survive Ay's initial blitz anyway and raikage would be caught off guard by Kisame healing (having no intel on it) so Kisame easily uses his water dome, then proceeds to merge with Samehada and absorb Raikage's chakras till he dies.