Eh Killer vs King would have been good, both of them are pragmatic, cool headed and basically a couple of murder machines
But Killer vs Hawnkins has a good theme already (scythe vs straw, basically a nemesis, also embodies the First Mate Duty and I'm leaving aside their backstory) and Jack would have been more appropriate as a Calamity fight imo (loyal, blonde, masked scythe users who are so similar and so different at the same time)