Gaara with some difficulty. Kakuzu's False Darkness could get around Gaara's sand defenses, which he would have to be alert for. But otherwise, Gaara's big sand attacks are capable of covering a wider area than Kakuzu's elemental attacks and it wouldn't be crazy to believe that the Kazekage could dispatch all of Kakuzu's hearts with a well-timed Sand Coffin + Funeral attack.
His control over 4 chakra nature types should give him the upper hand, also how versatile he is in controlling each element in separate bodies should keep Gaara occupied.
Not just that but, lightning > Earth... Gaara defense is sort of screwed.