Well, Calypso goes for what's efficient, usually. In the face of one person, he'd just BFR them the way he did to Preacher in TM2012, which I'll get to in a moment. But against multiple people, he'd use the thing he knows (or thinks he knows) would eliminate everyone at once, which is his transmutation. A good few of his wish-granting moments involved using transmutation, also. Ironic, since most of the game endings involving transmutation aren't as funny or well-written as the rest.
As for which BFR he's most likely to use on Hakumen, Preacher tried to come to the Calypso Industries company tower all "fire & brimstone" like, and Calypso sent the poor guy to an alternate dimension he has inside of a painting on his wall. Or rather, a prison block, suspended over a massive pit of fire, inside of a giant castle, in the middle of an open wasteland, which was inside of an alternate dimension he has inside of a painting on his wall. Preacher's clothes also got replaced with a full straitjacket set, for whatever that's worth.
This was literally the first thing he did when a lone person tried to come up and fight him. If Hakumen attempts to charge him, it's what he'll use.
EDiT: Going to sleep now, so I'll be back to respond to this later.