If I hand a machete to Jason Voorhees I think I'm at least partly responsible for the people he hits with it. I know what he's going to do with that thing.
Except you're not passing a machete to Jason Voorhees. That would be "double it and pass it to the next person who you know is going to pull the lever."
You're passing a machete to the next person in line. You don't know who that is. They may or may not pass the machete down the line. Considering I would not expect a person chosen at random to kill someone when handed a machete, it seems unethical for me to kill someone with a machete just to prevent handing it to someone else.
Or it keeps doubling even well after its surpassed the human population, and we all have to keep hitting "pass" in turns forever, and if even a single person gives up then boom.
I guess it comes down to the weight you give the word "possible" in your sentence. If possible means extremely likely (and there are logical reasons to believe so) then taking responsibility makes sense.
That's only if he's next in line though. If you pass a machete to someone who might one day eventually pass it onto him, is that as bad? I suppose at some point there's an ethical cutoff lol
The farther away he is the worse it is because the more people he gets to kill. If for some reason I absolutely had to pass the machete down the line then the best case is for the very next person I hand it to to be Jason. But even better if it's me.