User blog comment:Rafe Adler/"The Raid" Discussion/@comment-1975828-20170303075527/@comment-1031724-20170303213340

I keep thinking sooner or later one of them will do something the other can't tolerate, leading to him torturing them before they, or someone else, take him down

Though I find it hard to imagine when - Mr. Ketch never lets Sam and Dean know of the more sinister things he's done (killing Magda or the Secret Service agents, though he did express disapproval at them not doing so), and he lets them do things their way and "ties up loose ends" if they "leave any". He wants to keep up a good image so they'll be willing to work with the British Men of Letters, but sooner or later they might discover his true nature somehow