Towards the end of Black House, the foul Charles 'Burny' Burnside is killed by Tyler Marshall. When Mr Manshun, a servant of the Crimson King, finds the body of his former minion...
He looks back at Burny one last time, without much regret - there's a young fellow in upstate New York who shows great promise, and Burny was pretty well played out, anyway.
We're deep into Dark Tower storylines by this part of the book and knowing Stephen's love of references between books, I have to assume this refers to another anti-hero in another story, though not necessarily a Dark Tower story.
Can anyone suggest who that might be?