just pointing out, I don't think Kakuzu's lightning attack is equivalent to 2 Raikiri's, it seems that way because: 1. Kakuzu's attack includes two streams of lightnings so Kakashi had to stop it with 2 stream as well, 2. Kakashi's Raikiri is short range attack, it can not leave his hands, therefore even if Kakashi's attack were a lot stronger than Kakuzu's, they'd remain in his hand after cancelling out Kakuzu's attack, which appears to make them "equal".
also, Kakashi could be using only 2 Raikiri, jus split the lightning equally into each hand after gathering it.
btw does Minato know Odama Rasengan? I don't think the one he used on Obito was as big as Odama Rasengan.