The more I think about him the more interesting he gets. Like a lot of people might quickly go to what seems like an established contradiction between his epithet and his character... but he was totally willing to cut down a little girl to get the job done. The ability to reason (and compromise) is treated as a liability in the world of pirates, but that doesn't get him written off.
He's a good foil for Zoro because he's just as important for his captain, but provides a complement rather than a supplement. Selfish yet selfless vs ruthless yet selfless. At first I didn't like that the smile fruit thing goes toward Kid's character rather than Killer's, but that is how his character works. At least until it's necessary, he doesn't trip over something like that and it makes him stronger. He's a supporting crew's supporting crew, and as a right hand man only Katakuri makes for a better character outside of the Straw Hats.
