My guess is that Rumple is referring to the Blue Fairy. Seeing as Cinderella gave him a quill which she had enchanted that bound his magic. Effectively leading to Thomas’ disappearance, as well as Rumple’s imprisonment in the cave-cell that the dwarves had fashioned for him to ensure his magic would still be moot inside his cell. So that’s probably part of the history he’s referring to..
I’ll buy that. I wonder where exactly he would send them if they default, since nobody can leave Storybrooke. Or is that just the ever-looming threat that nobody knows he can’t make good on?