Pretty sure Onoki takes this although Kakuzu's elemental barrage will definetely pack a punch. If Onoki uses jinton, he will be a stationary target for those elemental barrage. Still Onoki does have powerful earth style as well. By hype he should be well versed with wind and fire style too. I give him the victory with high difficulty. His low stamina will make this a hard battle for him but flight will allow him to evade Kakuzu and weighted rocks can give Onoki a great offence as well as defence.