"I wonder how difficult it would be to just make a list of all the top blood purists and kill them.

They'd tried exactly that during the French Revolution, more or less - make a list of all the enemies of Progress and remove everything above the neck..." -Harry's internal monologue, HPMOR Chapter 7

"Amusing, but that was not your first fleeting thought before you substituted something safer, less damaging. No, what you remembered was how you considered lining up all the blood purists and guillotining them. And now you are telling yourself you were not serious, but you were. If you could do it this very moment and no one would ever know, you would." -The Sorting Hat, HPMOR Chapter 10

Well...well I guess it wasn't technically a guillotine. And Harry didn't make a list himself. But Harry did do it, and set it up so no one would ever know.