Which is really ironic, as my late father is the formal registered inventor of the Folding Crossbow.
https://patents.google.com/patent/US4926834A/en
No, this one isn't a folding crossbow, but it does seem powerful enough to potentially be deadly. It's raining today so I'll have to wait for a good weather day and find an old used slab of wood for target practice.
He had originally made 4 arrows for it, 3 with blunt end tips and one with a razor sharp arrow head meant for hunting. He never actually took it out for hunting, it simply wasn't powerful enough for that, but he would shoot those blunt tip arrows indoors at cockroaches (those big waterbug type roaches) whenever one would pop up. It wouldn't even penetrate the walls, it would just leave small dents, but it was his house and he didn't give a shit LOL!