Orochimaru would be the most likely choice - Kabuto wouldn't really register as a major problem in comparison, and between the other two threats, he'd take the one his sensei went after. Given how badly out of his weight-class snakeface is, he'd try to pop out of hiding and immobilise him with shadow or paper jutsus for someone else to get a killing hit in.
D for Drakensis
You're only young once, but immaturity is forever.
D for Drakensis
You're only young once, but immaturity is forever.