Bill Munny: You better bury Ned right, and don't go cuttin' up... Nor otherwise harm no whores, or I'll come back and kill every one of you sons-a-bitches.
Little Bill Daggett: I don't deserve this... To die like this. I was building a house.
Bill Munny: Deserve's got nothing to do with it.
[Aims gun.]
Little Bill Daggett: I'll see you in hell, William Munny.
Bill Munny: Yeah.
[Fires.].
Little Bill Daggett: You just shot an unarmed man.
Bill Munny: He should have armed himself if he's gonna decorate his saloon with my friend.
Answer: Not crazy, but maybe there's a bit of the Mandela Effect at play. There's no such line in any draft of the script, and it's not in any version of the film I've seen (including theatrical). In any case, Little Bill already knows that Munny is going to kill him, hence his line, "I'll see you in hell." If there was ever any doubt in his mind what was going to happen-as he lay there staring down the barrel of a shotgun, wielded by a man who'd just murdered a roomful of people-it's certainly gone by that point.
Will was pointing a Spencer at Bill, not a shotgun.