Suggested by iKnowledge Klarion has a lot of magical abilities so you don’t want to underestimate him but Kakuzu is still taking this in a close combat brawl. He was able to hold his own against Kakashi for a period of time which is extremely impressive and his monsters will keep Klarion busy as well. The mage just doesn’t have versatile enough abilities to really take the win here. Kakuzu wins.
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I’m not denying the powers & uses of the Akatsuki, but given how Klarion is strong enough in all his continuities to fight against Dr. Fate and other Lords of Order and live, his odds are better than you think. What is prohibiting Klarion from constricting Kakuzu’s veins and brain nerves with a gesture or two, thus leading to strokes and heart attacks for Kakuzu. Those are probably beyond Konoha’s medical knowledge to treat, so if that goes, Kakuzu is dead. Teekl will probably have dinner from him too.
Klarion definitely is strong but it’ll be tough trying to constrict Kakuzu like that. His super strength is considerable so it’s like trying to force choke Superman. In theory his sheer strength is enough where he should be able to resist that and keep on fighting